I would like to see the xr blocks for p7 heads actually enter the market. A big inch p7 would be a real power house.
Ernie Elliot makes an aluminum block for the P7. I believe it is capable of 440 inches. Never saw one, but it is listed on their website.

Gen III would probably be the most economical solution, but my admittedly distorted thoughts are, a hemi is not complete without a blower.