A 4agze with a w55 would be great in a AE71 or KE70.
Its hard to supercharge or turbo a 20v effiently because of the Quad throttle bodies, I'm not saying its impossible but its hard, Id stick to a GZE and mod that with a turbo instead of a S/C.
You can put a CAS (camshaft angle sensor)in place of the distributor on a 20v to solve clearance issue's.
SR20 could be a better alternative if you want bucket loads of power. If you want to know more about a SR20 do some research and see what you come up with and have a chat to IROKIN, he has a SR20 silvia and he would be able to help you more in the engine department.
You have a F6 so you should be knowledgeable of how forced induction works.
A turbo takes time to spool up, A super charger boost's from idle to redline but takes power to run.
15k will set up a AE71 to an awesome level no matter what engine you use.
Des. :D