Big Block Advice Needed

I t hink a bigger solid flat tappet cam, and the ported heads could get you where you want to be IF (a big if) the compression ratio is what you think it is. Pull a head and see how far down the hole the piston is. Those motor home engines were about 7 1/2 to one. I would recommend finding out what the cr really is, before selecting a cam.
And then after the cam and head swap, at least try the dominator tunnel ram. It's way too cool to sit on the shelf.