If it is a 72 340 and all original, it will have the cast crank and the 8.5:1 CR pistons as all 72-73 340's had cast cranks and low compression pistons.
To the OP, post dates and part numbers of the heads as well because 72-73 340's should have the small valve heads and if your engine has the large valve heads they would be from a 71 or older motor but are still an added bonus. Joe