You may be looking at this somewhat wrong. The advantage of a turbo engine is pure tq at a lower rpm and a broader rpm range of tq. To get high hp #'s a engine needs to hold torq to a higher rpm ( above 5250 rpm) then high hp #'s will be produced.
A street turbo 250 can be built simular to my 250 turbo project and expect to see with intercooler, 4 bbl, timing controls ect 400+ ft lbs torq from around 3k rpm - 5500 rpm @ around 10 psi.
Mine did make more hp than you can see in vids, I did not show all the vids.
The intercooler can ad 10 % more power, so in my case 35 more ft lbs tq would have been seen.
In answer to the second question the turbo 250 I did would pose a big challenge to a 300 HP 350 from a 70 camaro as they came back in the day as Z-28's. More tq over a larger rpm range.
