Well, I'm a collector of fine junque ..so it would be hard to part with a perfectly running engine. It would probably end up with my piles of fine junque and never get used. I find, however, whenever I part with fine junque ...it's assured that I'll have a purpose for it in the near future. I now look at all find junque acquistions as insurance against future needs.
I don't have great knowledge about the engines either, but my belief is that all the lower displacements share the same block 290, 304, 360, 390. The 401 has a distinct block that looks identical externally, iirc, except for the big 401 cast in the side.
Gary L. Allan, Sr.
If it ain't broke ..fix it 'til it is