@old_racer: thanks, Russ, for joining in and supplying some first-hand infos on (the now ex-)Wally’s-car.
Glad you were more knowledgeble than the kid’s other mechanic and detected the u/d-pistons. That mechanic should have listened to UTG, that turning-arround the pistons is a no-no at engines with valve-reliefes/domes (e,g. 6pack/Hemi)...otherwise that would have made to an expensive “experience”.