About the cheapest turbo off a factory rig would be off a Detroit. Its a Garrett TV8101. The one I had was 82mm. They will get to the 1000 hp range. Would work well on 400-500".

67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials