My 70 Duster build

In a 5M at 14 PSI i dont think it will be more than 220 tops @ the wheel but with the size of the turbo it will be torqey you need more turbo more boost and more fuel, i bet a good 74mm t4 turbo with an A/R of .84 on the hot side a set of 6 750cc injectors and a stand alone on a good tune with 25 PSI it will do about 450 at the wheel but then the lubrication on the engine will be an issue, you need to replace the banjo tube from the oil pump pick up to the block with a braded line with a an fitting in -10 size if my memory still good to prevent the cavitation from the poor transition of oil in that part of the oiling system!