I checked with JASPER and the only way they could get me a rebuilt 400 short or long block is if I sent them one to rebuild... So that not an option.
I got more info from the guy with the short block (link below). He took some pictures for me (below). It is a YS block dated April 21, 1971. The 71 YS block was apparently for 300 HP 400's backed by Turbo 400's. They put them in GTO's, Firebirds and B-body cars. He said he sold the heads #96 off it in years past... Said he thinks it's std bore but couldn't find any markings...
$1400 seems like a lot for a short block without heads... I would also have to assume it needs bored, new pistons and crank turned*(not sure what all that would cost). It's only 2 1/2 hrs away.
https://annapolis.craigslist.org/pts...675788752.html