The convertor is not a factory standard unit. Pull it off of the trans...it just pulls straight off, and check on outer shell for stamped or written numbers etc. Dont use that convertor until its been split and checked over, same for the trans. After sitting this long, the seals will have dried up and it would likely not work correctly.
Given the engine has a higher stall convertor, and it has headers, its likely there is an aftermarket cam in the engine. Remove the rocker covers and check if they are after market or not. Pull the plugs and use a bore scope to check for pop ups on the pistons etc.
Post a pic of the end of each head showing the casting marks.
Given the huge numbers of SBC engines built, it can be very difficult to determine origins.
I personally dont care about lineage, unless its a true "numbers matching" vehicle engine package...very rare nowadays.
Lets see the ends of the heads for casting marks and if the heads have angled spark plug holes that take peanut plugs....
