Hi Mike,
Happy Holidays and welcome!
You have already gotten a lot of good advice.
I'd like to also suggest a BMIHT certificate for your car (
https://www.heritage.org.uk/archive/certificate/default.htm) With that you can confirm originality of some of the major items, build date, accessories, etc.
Research and document thoroughly before taking anything apart and starting any work. No doubt previous owners have done work or had work done on the car, so some things might have been changed or modified already. Be aware that there has some parts have been superceded and certain vendors might supply a later item that's not 100% "correct". As an example, the trim insert around the windshield seal on our cars was originally bright anodized aluminum. Most vendors supply chrome plastic replacements (that shrink over time).
As to texts, check out Roger Williams "How to Restore TR4 & 4A" for lots of detail and up-to-date, step-by-step info. Parts sources are given, but focus on the British vendors, not U.S. unfortunately. Not to worry, you'll get to know them all pretty quickly!
Bill Piggott's books are probably best regarding originality issues. He has two in print that cover your car. One is an overview of the entire TR line. The other is focused on the Micheloti-bodied cars (TR4/4A/5/250) and has more detail.
I also recommend a more general, non-marque-specific book entitled "How to Restore British Sports Cars", by Jay Lamm. It's a good overview of the entire restoration process and is very helpful.
I'd recommend you focus first on safety, then on mechanical issues. So, tires, brakes and steering are probably the first concerns. Next is frame, suspension and drive train. Finally, engine, carbs, gearbox, hoses, belts, etc.
Cosmetic issues might be delayed while the rest is sorted out. For example, exterior paint can be touched up and seat covers can cover ratty upholstery, for the time being.
The hole in the driver's side floor (which tells me the brake and/or clutch master cylinder leaked, probably during extended storage, so those systems need checking) can simply be patched until you want to tackle a proper repair.
Your car will have a hybrid frame that's basically a TR4A front half with a different rear section to accomodate the live axle. These frames can have issues at the center, the so-called "t-shirt" pressing the exhaust pipes pass through. Often this area rusts, cracks and weakens. The rear segments of the frame can rust from the inside out, usually progressing from the rear end forward. At the front, the angular braces from the shock towers to the main frame rails often rust near their base, because there was no drain hole drilled by the factory (it's easy enough to add one, especially if/when the engine is pulled).
The Michelotti body has some potential problem areas. If the floor is rusted through, also check the rockers, the a- and b-bost bases, and check closely behing the fenders (by removing them and/or looking from inside the trunk & engine compartment). The vent scuttle can rust from the inside out, if the drains were plugged. Those drains dump water behind the front fenders, which can lead to rust there, as well (many extend the drain tube out under the car, right through the rockers).
You might seriously consider getting a frame reinforcement kits from someone like Revington TR (
www.revingtontr.com) or other vendor. This simplifies the process because all the needed items are included, not to mention some instructions! The kit is based upon Neil's experience in vintage rallying and his own factory-prepared TR4 Rally cars (he owns one or two of the originals). He has adapted kits for earlier and later cars.
As an example, one key area is the shimmable, lower/inner front suspension mounts, which are weak on all TR4A/250/5 and some TR6, really should get some reinforcement to be safe. The parts can be bought separately, or fabricted if you know what you are doing, or sub-kits are available for from several vendors. But it might be best gotten as a part of a whole-frame reinforcing kit from Revington. Roger Williams shows details in his book. Welding is necessary.
Yes, catalogs from various vendors are excellent sources of info. Victoria British and Moss supply the good ones here in the U.S. Moss' is also online at
www.mossmotors.com
But, also get the reprint of the correct factory manual published by Bentley, and the factory TR4A Spare Parts Catalog. These can be pricey, but have tons of info. You'll need the spare parts catalog with the original parts numbers to order from some vendors (The Roadster Factory and others).
To save on these and all books, watch on eBay for used copies. Or better yet go to Amazon.com where prices are often lower, especially for used books.
If you will be doing a lot of major work during a fairly short period of time, you might consider signing up for The-Roadster-Factory's TRF Car Club and/or Moss' Rebuilders Program. These have an annual fee but entitle you to regular discounts for the year.
A digital camera is really helpful, as are other organizing tools such as baggies, markers, tags, etc. For a full, frame-off restoration, a three car garage would sure be nice, so long as you don't have any other cars parked in it! /ubbthreads/images/graemlins/ooo.gif I've decided that the first step of my next restoration project will be several large, deep shelving units to store all the parts on! (Note: keep *everything* until the project is done, if for no other reason so that old, worn out parts can be carefully compared with new, to check for correctness.)
Do you have a local Triumph club? If so, they can be a good source of info and support!
Have fun! These cars are pretty simple and easy to work on.
/ubbthreads/images/graemlins/cheers.gif
Hey Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
