:D :D :D :D
1, having had both a 12a and currently a 13b, there is not much difference between the 2 engines.
a bridge ported 12a will beat a stock 13b anyday,......hell one of my mates 12abp 323 is quicker than my 13bbp down the quarter!!!!
2, rx4 4 speeds are still findable quite easy if you look in the right places.....www.ausrotary.com :D
rx5/121 5 speeds are also quite a good box and arn't too hard to find either.
expect to pay anywere between $200 - $350.
3, don't bother with a s4 turbo box for an NA 12a or 13b, your looking at atleast $400 for the box and will have to upgrade the clutch and flywheel to the s4 9.5 inch items.
if you wanna start pushing 300+hp, then look at this option.
4, yes its quite common to see people running up to about 400hp with a corona 4 speed, so this is another viable option.
5, $100 for a 6 port 12a, which ancillaries means its f@$ked.
6, another option with the cross member/sump deal is to make a custom sump and oil pick up!!