SNIP
Turbo engine is engine above, holley 350 carb modified for blow through, spa manifold, IHI turbo from ford turbo coupe should build boost fairly low. external wastegate, probably no more than 8psi. just don't know how blow through and off roading will work
Why not inject it? The power level you want to make is well within what a TBI of off a BBC will support - and this eliminates all the issues with fuel distribution. Off angle approach - no more issues with floats.
Not sure if the holley TBI supports boost but the megaasquirt does - a bit more work but less $$.
