um....
you don't.
you're going to at LEAST have to change the engine harness.
if you dont want to convert it to obd1, youre gonna have to:
1. hack your dizzy
2. hack your injectors
which might not work, and will probably look like shit.
just buy an obd1 dizzy and obd1 injectors.
also, you can use your stock obd1 ecu if you absolutely have to, but it'll be shitty.
best bet is to get a p30 or a chipped p28, or get an obd1-obd2 jumper and use the 99-00 Si ecu.