And thanks to Curtis and Moparmadduck.
I am producing 4-manifolds:
RB-1, 413-426-440 big runners, single plenum, single or dual carb
RB-2, 413-426-440 big runners, split plenum, must be dual carb
B-1, 383-400 big runners, single plenum, single or dual carb
B-2, 383-400 big runners, split plenum...