[Rotary Evolution]

i would chalk it up mainly to improve fuel economy. the older rotaries had the angled compression pockets and the revision came about shortly after making the pockets in the rotors equilateral/fuel injected(with the exception of the original 13B RX4/REPU/GSL-SE engines).

the change actually came on series 4 jspec engines so it came about in the '87 era.

i've used the various combos in just about every compression ratio engine(always matched housings though), turbo and non turbo and never really noticed any drastic side effects. but i never did any back to back comparisons, just too much work for sake of testing. i would tend to think the later revision should improve performance but is less forgiving with aggressively advanced timing.

if you're trying to get every ounce of power out of it i would probably use the later series housings, the chrome is superior anyways for the added benefit of longevity. but i wouldn't expect much noticable gains in performance.

if the housing is going to be narrowed for use in a 12A engine, i doubt you will get much feedback. the position isn't drastically different so i doubt you will have much trouble with it, especially if using alcohol.