wiki confirms for posterity even if trans is same model, bell housing/front cass is different, with a diagram. it's just only listed under the "bell housing" page and not the transmission one.
have seen the roadster seating position and all i believe it has the selector farther back, just by eyeballing it.
i'd put the whole r16 driveline in all together, but when i see next to no research on it, it does make me think something like a sump/pickup tube is in the wrong place. not to mention roadster guys aren't exactly out hunting the A15s, so it must not be worth it.
i'd love to have enough free time to even halfass fix this motor, i'm hoping the dozens of smoke-belching freeway miles aren't screwing the innards up too badly or anything. i just can't take the time off to fix it. if you have recommendations for a basic ring kit, i'm all ears. i can at least buy it and look at it.
did get a possible lead from putting up a WTB ad, Ratsun ftw.🤘