When converting a '72 914 from tail to side shift tranny, are there any modifications required in the tunnel -- in particular increasing the size of the hole in the "cross brace" the rod passes through (looks like about 1 1/2 to 2 inches in diameter) approximately 9 inches from the shifter?

I've done this (and researched it a fair amount beforehand), and I don't think there are any tunnel mods required. You do (of course) have to change the bushing at the firewall (the one from Tangerine is great), but the tunnel itself and its innards should not require modification.

Basically you need everything from the shifter on back (rod, bushing, tranny, etc.) to be the side-shift version in addition to the later model engine support bar.

Thanks again for your prompt helpful response. I have all the Tangerine equipment (quality parts). Struggling to adjust the shift mechanism. The nylon ring and pinion have not worked for me -- turning the pinion is too stiff and it appears to skip on the ring rather, or the ring is slipping on the shaft.

I used both of those Tangerine parts (bushing and shift rod adjuster). They're excellent examples of engineering, but I also struggled for a bit to get everything where it needed to be and working. I don't think I had trouble get the adjuster to work, though.

You've got Chris' install and usage instructions, right? Maybe if you post some pics it might help explain what's going on...

I actually found that I DID have an interference inside the tunnel after converting.

I didnt think I did, but after another person on this forum posted that they were opening up the tunnel to expand the hole I decided to have a look.

I used a large hole saw to cut an access hole and found that the shift rod would rub on the side on the hole that the rod goes through.

I opened up the hole with a 90 degree grinding tool.

My car has a rennshifter so I dont know if that makes a difference.
Maybe the stock shifter doesnt have the interference.

After moving the rods forward 1/3" and the shifter anti-clockwise 1/8" all gears are now functional. Car is now very drivable, but expect to make one more final adjustment after further "wear in".
Thanks for your advice.

Are you originally from the UK?

Glad it worked out Did you end up having to move anything about or enlarge anything in the tunnel?

Not from UK, but from the "Camelot" country of Rhodesia -- left in 1959! Why do you ask?

Did not change anything in the tunnel. Think the rod is just touching the hole edge when in 4th gear -- will be part of my final adjustment anti-clockwise adjustment on the shifter/rod connection.

Here in 'merica we say "counter-clockwise" (and our friends to the North, too). Yes, Rhodesia has gone the way of Camelot. Well, a belated "welcome" to you (nearly 60 years later), and glad it all worked out

Could be wrong but I think pelicanparts (and others) have a conversion bushing.

moved the rods 1/4" further forward, total of some1/2" of the rear splines now outside of he UV joint coupling. Went for a test run, -- all good