Hi again,
I suspect that even originally Triumph Spares didn't sell those pipe fittings separately, but as a small sub-assembly that included a short piece of piping with the fitting already flared on.
You might check
www.rimmerbros.co.uk/ and
https://www.moss-europe.co.uk/MossUK/ for small parts like these. The small stuff isn't too expensive to ship from England (the big stuff gets pricey). Larger items like the longer runs of fuel pipe can be bought locally and shaped to fit, I'm sure.
I suspect my TR4 has the original "bung" in the fuel tank, but really don't know if it's British pipe thread or US. FYI, even if it's BSP, that's so close to USP it's a common practice to use one in the other. In fact, some do this deliberately since it makes for a connection that's unlikely to ever shake apart. A little Locktite thread sealant can be used to insure no leaks, but the two threads are close enough it's usually not necessary.
I took a different approach with my TR4. It's certainly not "original", but I've now got a USP-thread-to-AN6 fitting on the bottom of the tank, an AN6 hose running from that to a Fram FP-1 filter, then to an elec. fuel pump, and next all the way to the engine compartment where there is a Holley fuel pressure regulator, then on to the carbs. Using stainless steel braided AN6 "aircraft" hose throughout makes add some security against any rock damage leaks, etc. (and it looks pretty cool!). A downside to using stainless steel braided hoses is that they are pretty abbrasive anywhere they might rub. I fitted larger dia. rubber hose over the section where it passes through the frame rail and used a lot of rubber-cushioned clamps elsewhere to prevent any rubbing.
Some (all?) TR4 have a second bung in the bottom of the tank, on the opposite side, intended as a drain. I've noticed TR6 tanks without the second outlet, but am not sure about other models or exactly when the change occured. I mention this because it would be possible to use as an outlet, if the original one were too messed up. Eventually I think I'll add a second AN6 pickup there on my car and use a tee to feed the system from the tank in two places, one on each side, which should prevent any surge issues when goin' round corners faster than I should (a TR4 tank already has surge baffles inside, too, which certain later cars don't).
If it is really impossible to find any sort of fitting for the tank, that will thread into the bung properly, it wouldn't be all that hard to remove the bung and replace it with one that has more widely available threads. The tank metal is pretty thin stuff, and pretty difficult to weld. I think originally it and it's fittings were all soldered together. But brazing will also work. A radiator shop might be helpful, if you don't have the tools and skills to do the soldering or brazing yourself.
Of course, be extra careful welding, brazing or soldering around any fuel tank. If it's had fuel in it lately, it should be repeatedly rinsed out with soapy water to insure there is absolutely no remaining fuel or fumes. Even then, carefully test before getting close to it to do any work with a torch.
And, be very careful trying to loosen any of the fittings, top or bottom. They often rust/weld themselves in place and it's way too easy to torque the soldered bung right out of the sheet metal. (Don't ask how I know!) Use lot's of penetrating oil on the fitting, possibly over the course of a week, before trying to remove it. And, try to avoid applying heat - to help loosen the threaded fitting - just a little too much will melt the solder.
Before investing too much time in an old tank, you might want to closely inspect it inside to see if it's really usable. Rust can cause all sorts of problems in the fuel system. Any seriously scaling rust might mean tank replacement, as it will make for weak points, potential leaks and flkes of rust can cause havoc in the fuel system. Surface rust can be neutralized and then coated with special compounds just for the purpose (
www.eastwoodco.com sells fuel tank restoration kits). But I've heard this process is only good for about 5 years additional tank life before the coatings start to fail, too, and then they might themselves cause blockage or restrictions in the system.
Replacement tanks are available, if somewhat pricey. Some appear to be pretty close to the original. If changing it out, to me it makes sense to go to aluminum or stainless steel (altho the latter would be too heavy, IMHO). I've toyed with the idea of making up a tank/fuel cell from aluminum, but am not very knowledgeable at shaping and welding the stuff yet (so might take a welding/auto body class at a community college and make it my class project). We'll see.
Back on track, hopefully you can find the fittings at one of the British suppliers (or elsewhere). You might also call or email John Swauger at TRF's second level sales line, see if he can suggest some alternatives.
/ubbthreads/images/graemlins/cheers.gif
Hey there 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! >> 
A friendly reminder - be careful what links you click on here. If a link is posted by someone you don't know, or the URL looks fishy, DON'T CLICK. Spammers sometimes post links that lead to sites that can infect your computer, so be mindful what you click.