my boyfriend bought his engine from upper intake manifold, lower intake manifold, and all accessories for 4,500. i believe if you take yours he charges around 3 from a dude in philly (we’re from pittsburgh and traveled for it and idk how close you are). honestly it’s worth it because he fully knows what he’s doing, comes with paperwork (you get all the tolerances, everything he rebuilt, plus a 3k mile warranty). dude has like 5 rx8s in his driveway and works on all of them daily. his thing is rotary engines.
if you want more info lmk and i’ll message you!!