Originally Posted by ciper
If I may speak for the OP for a moment, no matter the engine platform he will need to remain turbo. Remember aircraft reach high altitudes where the air pressure drops. Every 10k feet is like 2/3 the power at sea level. A low boost turbo will keep the engine from "leaning out"
I think the most important question is "What engine management will he be using"
If he can go aftermarket my vote goes for EJ20 since they are a dime a dozen.
My second vote goes for an intercooled low boost EJ25. A 99+ ej25 will probably already make 170hp since he will mount a custom exhaust and even 18psi manifold pressure (+4 over sea level) would probably put it near 200 with an intercooler. The RS25 guys have plenty of experience turboing the EJ25 before the 04 USDM STI came out.
I think the low boost EJ25 is going to be the best bet. You are exactly right about the altitude, the turbo is needed just to at least maintain sea level performance. I plan to just use the stock ECU and use a programmer of some variety if possible to tweak the performance.
Now if I can figure out the actual final weight, we can determine if the project can possibly run.