[screamingchief]

If you wanna gain some IH for better spring selection,and more max lift clearance,just use the valves from the 4X-4h heads in those 6H heads.

That move alone will add at least +.150" IH to the 6H heads,probably more.

The 400 heads valves are typically 4.980" long.
The 455 heads valves are typically 4.810" long.

Only catch to that "trick" is the need for corresponding longer pushrods.

And should you opt to use the solid lifter cam,lifter choice can affect that pushrod length as well.

Personally,for a "milder" combo,I'd opt for somewhat lower compression ratio,bit higher boost,and as much lift as I could get without running into P2V issues.

Bruce & Brad's cam suggestions both are in the ballpark IMO,I'd also opt for a rocker like the HS 1.65's which measure closer to 1.7 ratio.

Peak head flow numbers likely wont be too big a deal in a "budget" combo like this.

The boost is where the bulk of the peak power will be coming from.

12 lbs like Baron mentioned sounds pretty reasonable IMO.

But I dont claim to be a boost expert either.

Just wanted to point out that valve swap deal as an option here.

The OP said he wanted to use as many "on hand" parts as possible.

HTH

Bret P.