You don't need to lower compression with modern ECU technology, you just need to control heat and spark very well. The N47 has exhaust liners which will disintegrate and eat your turbo so you're better off with a square port exhaust for a turbo. The P90 will lower your compression if you have dished pistons (well it'll be lower versus the N47/N42 regardless of piston choice). 8.3:1 is a good compression for an L28ET which is what the N42 with dished pistons will give you. I think the P90 is around 7.5-7.8:1...but you can make a ton of power with the P90...just won't be as peppy out of boost.
Try to get an N42 if you can...but the P90 will work. You need to get a good intercooler and I would definitely consider running methanol injection. I'd personally swap to a wasted spark crank trigger like EDIS or GM coil on Plug (and you can run the GM plugs with the EDIS box so you don't have to make custom ignition wires.)
If your power goals are for less than 300 HP it's not that bad of a build....just factor in a high flow fuel pump, turbo oil pump, oil cooler, intercooler, spark system, injectors and your ECU. You can run it with a megasquirt I which is pretty affordable, but you'll need to make mods to control spark. Megasquirt II is a bit easier to work with. If you want launch control/antilag/two step then I would go megasquirt III it's kind of overkill for most builds but it's got 4 switched inputs so you can have two tunes, datalog over Bluetooth and a bunch of other shite.
if you just want 275ish HP... slap on the P90 and start buying the other parts.
FYI the hardest turbo part to source is the exhaust manifold...once you have that it's pretty easy to find the rest.
1977 280Z, 3.1L Stroker , Ported N-42, Lonewolf performance Intake, 3 into 2 headers, Megasquirt I-V.3, Kumho Ecsta XS's (supa sticky),
This 280 ain't no old lady