Welcome to CHR!

We’ll need a bit more information to adequately address your situation –
What heads are you using? What head modifications did you have done? Use of a cam of the size you described (Comp Cams 12-430-8?) with the stock heads will be a major disappointment on several fronts – First, the 322 pounds springs (Comp Cams 986-16?) you selected will address the pressure issues associated with this cam but unless you’ve had the proper machining performed, the retainers typically will hit the guides/seals around .470. Second, if you have the early cast iron 305 heads have 1.84 intake 1.50 exhaust valves – real small.

This cam requires the use of a thrust button & wear plate.

What stall speed is your converter?

What’s your rear end ratio?

What’s his engine in?

What brand “single inlet” intake manifold?

Headers?

My insides tell me that you’re over cammed and a bit over carbureted. As to the turbo – with almost absolute certainty I can tell you that the only thing a turbo would do for you is grenade this engine.

Give us some more info and we might be able to help you achieve what you’re after – bear in mind that you’ve maybe started this project backwards..