Hey Uncle Phil, why are you so conservative with your L76 power expectations?.
You say you expect 320 RWHP with a cam.
It's almost common place for a cammed L76 to be around 380 - 400 RWHP, and that's with a relatively mild cam.
Keep in mind the tuners are unraveling the mysteries of the E38 and are now getting excellent results.
The LS7 sure would be nice but like Bobby said......a 402 ci L76 would be cheap by comparison and a lethal combination.
I am of the belief that the 5374 heads on the L76 will work much better with 400 cubes.