Replacing a 216 with a 235, is almost a bolt in replacement. No need to replace any of the drivetrain as the 235 uses the same bell housing. You can even use the same flywheel and clutch as long as you use the 6V starter. No issues using the 6V starter on a 12V system as I’ve been doing it for 4 years.
If you get a later model 235 (late 55 thru 62) as Jerry pointed out, the fan will be too low to effectively cool the engine. A fellow bolter “Pre 68 Dave”, invented and sells an adapter plate to relocate the original 216 water to its original position . I bought and installed this plate on my ‘59 235. The installation was fairly easy and it works perfectly.
If your interested, you can PM “Pre 68 Dave” thru Stovebolt.
