Hi I'd say a T25 or T28. Both have t2 flange which are common turbos. I'm guessing an a/r of about .48 or .64 on the turbine. Any bigger would be laggy. Blow through and suck through have their pros and cons. Suck through is generally easier to set up and tune, but cannot be intercooled and the turbo needs to be carbon sealed. With positioning it don't think it really matters as long as the turbo gets oil and it can return back to the sump. General rule is keep inlet cool and exhaust hot, so if you can fit that into the build it should not be an issue.