The Megasquirt manual, http://www.megamanual.com/v22manual/mtabcon.htm, offers some insight on injectors and has some calculators.
Easiest way to match up a turbo would be to study an engine with similar characteristics and displacement as your engine. If you're doing a 1.8L 8V, you may look into turbos from a:
2.3T thunder-bird/mustang SVO
1984-1989 300ZXT
Eclipse GST,GSX/Talon TSI
EVO Lancer
20V 1.8T Jetta MKV
Or if window shopping for aftermarket turbos, T3 50 trim, possibly a T3 Super 60 trim.