S70/V70/C70 T5 cars are not rare
Ive actually modified 2 for ostrich and both have been rock solid
Just look for ths T5 models of years 97 and 98 amd you should be sweet
See what the drifters and drag people use, they have pretty high standards usually for tuning amd gauge the interest of the tuners
If they arent interested then find someone who is.
I would completely shelve the idea of using an NA ECU, its a compromise AND you will pay more to have it modified than to just get the right unit from the beginning
Im using an auto ecu flashed to manual as we speak, no major board differences and are far closer matched than a turbo - NA computer
Also whats interesting is just how bad the ecu actually controls boost, ill probably bypass the ecu managed boost control and run a paralell standalone system later on down the track
Ill have mine tuned by trent @ Chequered Tuning in Melbourne, he has done at least 1 850R that I know of so far with great results