I just finished a swap from a 235 to a 283. I had to find a bellhousing that matched the rear motor mounts and had to modify the starter hole on bellhousing as the new starter is bolted to block on 1965 283. All I did is enlarge hole a bit with burr. I the bought front motor mounts from Grumpy's in Phenoix Az. They attached to the front of block in exisiting hole and also attached to crossmember in exisiting holes. It really was quite easy on that part. As for the clutch/driveline. I used the old clutch fork and NOS throw-out bearing. The pressure plate from 6 cylinder was still good as was the clutch plate and they bolted right to the flywheel on the 283. Perfect match. The motor mounts were 115.00 and some change. I am now waiting on a throttle linkage as that will be your next problem. I ordered it from Carter's. They say it is everything from foot pedal to carb. Can't make the old one work. See thread on throttle linkage that I asked earlier this week. Great help on that one. Hope this helps.

Kurt