They are not a 4 bolt main block, but the "C" scratch on the back of the block shown in Marc's photos indicate a 428 block often used in a CJ or PI application. The four bolts around each exhaust port are unique to CJ heads. By itself, without any work, the block alone is worth >$1000, and the heads probably around $600 for the pair. Crank is probably good for $300-$400. So the fact that Marc paid $700 for the whole engine is a screaming deal. Now, add in the fact that the serial numbers stamped in the head show that it was originally from a Shelby Mustang GT-500KR, and that the original car was around as recently as 2019 according to the latest SAAC registry, and you have an extremely, extremely valuable engine to the right person. It sounds like the car may be local to Marc. If I was him, I'd be looking at two possibilities: Either sell the engine to the current owners of the car so they can put the original engine back in, or buy the car (especially if it's in pieces) and restore it. Personally, I'm not a restoration guy, but the story behind this engine is too good to pass up...
