Yeah you can run a s1 rb25/loom/etc from a rb20 ecu... there may be a few minor wiring changes though. Also as said above, you'll need a window switch to run the VCT.
Why are you running a rb20 turbo on a 25? They flow less than a 25 turbo and won't spool up much quicker...
If your going to stick with the mines ecu, you'll need to put rb20 injectors in it, rb20 tps and a coolant temp sensor from memory.
Personally, I'd buy a z32 300zx ecu, get a nistune board installed and plug that into the rb25 loom, then ditch the rb20 turbo for at least a stock rb25 turbo.
What do you want from it?