Most OEM turbo's for 4 cylinders will fit. I'm using a WRX turbo. You'll probably have to re-clock the turbo to get the inlet and outlets to point where you want them. The hardest part is making the exhaust manifold, but using a stock Focus header with a small adapter plate/pipe is a good alternative.

The main problem with stock OEM turbo's is they will run out of breath past 9-10psi. At 7psi I did 190whp, and at 9psi I did 200whp, not a huge difference. But if you just want a easy 200whp with quick spool, coupled with the low cost of buying one used, they're a good buy.

2000 Rio Red I4 Cougar 200whp & 210wtq at 9psi 254whp & 276wtq with NX 35shot WRX TD04 Turbo, Cut Short Shifter, Strut Tower Bar, 17" ZN Wheels, Roush Springs, Starion Intercooler, NX 35 shot, HKS SS BOV, Full 3" exhaust,StreetFlight Chip