whoa whoa whoa
all that effort to supercharge, tsk tsk, let me introduce you to a friend of mine, the turbo-charger

just jokes but curious why you prefer super?
ill tell you a bit about my motor as it should intrest you:
i have an a15, using fuel injection and twin turbos (maybe not necessary to use twins), but tiny turbos, 1000cc diesel diahatsu models, my car will spool the instant you put your foot on the accelerator, the only time it wont hold boost through a gear change is if i change to 4th at less than 60km/h (i.e. really labouring the motor). point being i feel i am getting supercharger like delivery of power from a turbo, but from a turbo, and it will hold plenty of boost at high revs still
anyways.... i am running 10psi boost with stock engine internals (intercooled), using a delco computer with a factory a-series manifold, i did my conversion as cheap as possible, fitting all the camira sensors and even throttle body up, the only expense was tunning which was plesently only $300
it sounds like you are willing to spend a lot more than i was though so this might not be what your after
hmmm to answer some of your questions.. i have been blowing standard a-series boxes with my setup... and am currently installing the dellow conversion to fit the celica box up, its either do that or get a 63A gearbox which is a facory built a-series box that has l-series internals, so basically should handle your power (but these are rare and pricey)
i think you made need something better than the clutches that are on the market, as i am using what is the a15 heavy duty clutch and i dont think its really suited to my power/torque let alone the power you will achieve
also a h190 diff from a vanette is a good option, easy to modify to fit and doesnt need cutting (disc brake conversion easy also), though lsd's are rare and highly priced for this diff, if you want to spend the cash its probably worth getting something cut
other question is what purpose is the car for anyways? street or race and what type of racing?
also for intrest its possible to get a-series electronic dizzies, so no need to go modifying an e-series one, all i did with mine was weld up the mechanical advance and fit the camira module in place of the a-series one and hey bingo i had spark
hope i didnt come accross as a braging knob about my setup
p.s.
...how are you injecting it?
and note my head is stock a15, unfortunately i have no power figures on it yet as had off-fuel during tune and boost was a little too high so they didnt want to push it ( i run 98 octane in mine also)