BTW, I believe another TC member, DZAUTO, put a 350 crank into a 307 (same bore as a 283). 307s may have the same sized rod and main journals as a 350 though, I dunno.
I've never put a 350 or SB400 crank into a 283 block. Although, it's my understanding the later 283 blocks (mid/late 60s) have sufficient clearance. I have put 350 cranks into small journal 327 blocks simply by having the mains cut down (as well as a little cut off of the flange between the rear main and rear seal journals). And of course, EVERYONE is familiar with a 400 crank into a 350 block (makes a 383). A 350 crank into a 307 is a too easy drop in. With a .030 bore and a 350 crank, this makes about 336 from the 307, which is only 14inches smaller than a 350, thus you would build one of these just as you would build any other 350.
Earlier I mentioned that the later 283 blocks had more clearance (for crank counterweights) than the earlier 283 blocks. I believe this increased clearance in the later 283 blocks occured when the 327 was introduced. The 327 blocks do require more clearance, and so when they were cast the molds for the 283 blocks were changed which gave them the same (or similar) added room for a bigger crank.
Also, I personally have never put a SB400 crank into a a 283 block, but the machinist that I use says he has had customers who have had him machine a 400 crank to fit into a 283 block. So, obviously, it can be done. Also, I have helped a friend build a 383 using a small journal 327 block and a 400 crank. The 400 mains were cut down to 350 size, then the 327 block was line bored to the bigger main bore size of a 350 block. Actually, it was a rather straight forward process. The 2 bolt main caps were retained but the longer 350 bolts (actually studs) were used. Made a good engine! This engine was specifically built this way so that he could retain his original matching number 327 in his 66 Vette. His engine did have one easy give away, it had a 400 balancer on it!!! At the time, he didn't know about using Mallory metal to do an internal balance so that he could have also retained his 327 balancer.
A few years ago, I built a SB400 for my 56 Vette and had it internally balanced specifically so that I didn't have to use that 400 balancer (which is a dead giveaway that you have a 400 (or 383).