I'd like to get some form of an overdrive in my 544 without having to carve up the tunnel. Is there some other transmission that's easy to find and hook up to a B20 that might work? Would the clutch have to be cable or hydraulic operated.

The Ford type 9, 5 speed, can be used in the Amazon but I don't know about the PV. Type 9 is rare in USA, Ford Merkur, and is very popular with the MGA people. The M41 has to be searched for but the tunnel mods aren't too onerous. Lots of how-to's out there. B20 uses cable but the B18 bell housing can be used to give you hydraulic clutch. I don't know which is the easier to use when converting from the PV mechanical system, probably hydraulic.

The 122/1800 bellhousing that's used with the hydraulic clutch is the same bellhousing that's used with the B18 PV. So, assuming the PV in question has a B18, no changes to the bellhousing nor clutch linkage are required.

Cameron
Portland

Yes, as Cam says. I should have used "if" rather than "when".

The main difference is the output shaft in the transmission is longer if it’s designed for the overdrive
I think the rest of the box is similar with the addition of the overdrive
I added one and shortened the first half of the driveshaft in my Amazon and run dot 5 silicone fluid not 3 or 4 in the clutch
I switched the brakes to dot 5 and it works ok
I just park it lots and didn’t want water in there or paint issues from the dot 4 or 3

If you drive it hard your brakes might be a bit mushy or may boil
The clutch isn’t an issue I’ve found the rubber seals last way longer particularly the clutch ones

Finding the trans to use might be hard

Later 122s about 69 or so used the cable I think.. 67 was still hydraulic

The cable means you don’t need to deal with leaky master and slave clutch cylinders
I went through rubber kits like crazy then swapped clutch to silicone and it went 20 years without a failure