I think I still have a set of the inserts to use a 350 crankshaft in the 400 block.
372 cubic inches- - - -we built those destroked 400s to stay just under the 375 CID limit at the track we ran in Merced California, back in the early 1970s. One guy ran a big block engine that he claimed was a 366- - - -but he was known to swap in a 427 at about midseason when the points race got tight.
Jerry