I'm in the middle of the same swap - here's what I found:
My 235 is a 58-62 and the boss cast on the left side of the block for the throttle linkage bellcrank is farther back, and the stock gas pedal to bellcrank linkage will be too short, and the linkage to the carb will not be in the correct place vertically. I'm going to fabricate a bracket to put the bellcrank in the right spot.
Drilling the mounting holes for the front mounts might not be as easy as it seems - that's what I was going to do to mine BUT the stock front mount also has rectangular cut-outs in the bottom to fit the motor mounts. Yours may have the cut-outs, but mine did not. Changing the front plate is fairly easy except for 2 things - pulling the crankshaft timing gear and removing the 3 flat-head screws that hold the plate to the block.
The 216 crank gear had 2 tapped holes to allow a gear puller to be attached to them; the 235 gear did not have tapped holes, which means the gear puller fingers must fit UNDER the gear. This is a problem as there is very little clearance between the back of the gear and the plate. I had to grind the back of the puller fingers (a no-no) to get under it. I was lucky as it came off without much problem, but there are horror stories of gear teeth breaking.
The flat-head screws are a problem in getting a large-enough screwdrive with sufficient torque to lossen them without the screwdriver slipping and messing up the slot. Again, I was lucky.
Good luck, the swap is worthwhile
