The D-type overdrive is what was originally made available with your car as an option, & is easier to install. I've experienced no problems with mine.
Also the OD with your car had the column-mount OD switch, which is really the best.
If you find a D-type OD, you'll need
-OD wiring harness (really, just get one & save time & muscle spasms, & you'll get the correct color-coded wiring which will make a HUGE difference to you someday)
-OD column switch
-OD relay (mounts next to the horn relay)
-OD reverse inhibitor switch (goes on transmission top cover)
All those are available from Spitbits in the US.
-Possibly the bracket for the OD inhibitor switch
-OD rear support bracket (2 parts, a y-shaped yoke & the little platform it sits on
You will also need a shortened prop shaft. Best is to just get a salvage-yard propshaft w/attached yokes & have it shortened & balanced, so the swap is easier. Put in new U-joints before it goes in.
Vinco transmissions in Atlanta used to be great for remanufactured OD's, I think someone said they're in Florida now.
That is not the original fuel pump, but if it works, let it stay! There are some defective replacements out now.
The fuel lind from the pump to the carbs is making a long hop in your car. The fuel line is supposed to be basically two metal lines joined by a short piece of rubber hose. The section attached to the carbs is OK. But it looks like the section attached to your fuel pump broke or was cut off at the other end, & the long piece of rubber line was put in to bridge the gap & was routed over the coolant hoses to keep it away from the fan. See if you can find a replacement salvage yard fuel line for the pump/spark plug side: it comes from the pump, has that funny hump around the distributor, then stays close to the side of the block, makes a 90 degree turn & runs across the front of the block (& is held there by a little clip with a bit of rubber between the clip & fuel line), goes past the right side of the front of the block a bit & ends. Some folks bend new ones out of steel brake line, but the internal diameter is smaller.
The breather setup between your valve cover & intake manifold is a little wonky, but I suspect at some point someone was unable to find the breather valve (called the 'emissions valve') that is supposed to go where the little filter is now. You can find the emission valve & little 'z' hose easily these days from various suppliers.
Do you have an electronic ignition? I'm trying to figure out what's up with your coil wires.
That is the correct distributor for your car: a Delco (identified by the flat-topped distributor cap).
Your car's exterior is red, but the engine compartment looks like the car was originally Damson! The paint code will be on a plate on the driver-side door jamb (if the plate hasn't disappeared over the years).
Someone's done some nice pretty work on your carbs.
After you get your fuel line sorted, probably the next important & most rewarding thing you can do will be to re-rubber your suspension. You might look into some of the polyurethane kits available now: some vendors have them in different firmness, & a softer polyurethane kit will be just right for your flying cookie sheet.
Check the rotoflex couplings in the rear. If they're cracked, replace them immediately or the bad thing will happen.
Edit:
Probably the most important thing for you to do RIGHT NOW is to oil the trunnions. They can fail catastrophically, modern replacements are not as good, but the originals will go pretty much forever if frequently oiled. Also, drain the gearbox oil & draw out the differential oil, then fill them with new oil. The diff & tranny are monsters if they go. There's a lubrication guide w/lube specs at
https://www.britishcarforum.com/tikiwiki/...brication_guide
Sheepskin seat covers for your sports car! Groovy as the day it was accessorized!
Great car! Have fun, & drink plenty of fluids.
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