nytrdr24
+1y
there are several post in the engine section about rotary swaps, although most are for 13b's.....nice thing on the 12a is that any associated wiring should be simpler than that on a 13b. you'll have to fab engine mounts, not sure on the frame x-member, but the trannys are interchangable between the b2k & b22k trucks and the n/a rx's. I would use the trucks tranny as the internals are stronger, but you may want to swap out the 5th gear for better mileage @ hwy speeds. you'll have to swap the bellhousing out on the trannys, but that is about it. also there are some nice little manifolds for those & the n/a 13b's so that you can run a side draft carb on them...anyhow, that's all I know for sure, there is alot of good interchange info about mazda stuff on solomiata's site, mazdatrix, & mazdatrucking too that can supplement what you find on here.
good luck!