the turbo off Jap S15 silvia (Spec R) says ballbearing T28 https://en.wikipedia.org/wiki/Nissan_SR20DET
Is the part number still GT2560R?
 

Jamesmk2 , just for your interest on the fiesta RS1800 intake , i pulled mine out of the dungeon and quick fitted to my mk1 van... dust and all..i needed to cut a corner from the mounting which won't weaken it to clear the factory alt bkt (blacktop) , and the throttle body looks like it will hit the cam cover. . I'll fit a Focus Sport 65mm tb there tmoro and see what's where. Also it just clears the bonnet by not much (bout an inch) .
Looks like the van is due for its 3 monthly wash again !!!

Also a Silvertop cam cover has the appropriate relief slot for such a manifold throttle body whereas the blacktop don't got that slot. .

Would be cheaper to drop an SR20, can't deny the ease of it all, cheap power

I also have a Megasquirt 2 running my NA Zetec on GSXR throttle bodies, there is heaps on info on the web for setting it up to suit your application and the possibilities seem endless if you like mucking around with that sort of thing.
I built it up as a project with my teenage son. (the young ones have better eye sight than me) then wired it into the car. I nearly fell over when it started first kick of the starter.
I couldn't believe how easily it was to get a basic tune with EFI Analytics tuner studio and wide band sensor.  that allowed me to comfortably drive the car for a while and sort any teething issues before I get a dyno tune.
You need to enjoy the challenge of a project and follow the instructions carefully and you won't go wrong.