So long story short, was told this guy has a TA/AAR block and turns out to be a 1979 dated Mopar Performance over the counter block and has been sitting in his shop since the early 1980’s. Now I know a little something about the ‘R’ blocks produced later on, but nothing on the ‘X’ ones. It looks to have a standard bore set of 340 pistons, but the guy will double check the bores when he gets back home tomorrow. The 4-bolt mains look super beefy and dang, it felt heavy like a 440 block.

So my question is:
Are these desirable?
How much hp/tq are they good for?
Is there a value to owning one or just sell it?
Thanks in advance.