[COYBILT]

All the engine choices you have picked are great candidates. My only advice is Do Not stick l92 heads on a 6.0L. Especially in a heavy car. The port velocity isnt there, The l92s have vvt to take care of the gigantic intake ports of the l92 heads. The l92s also have a larger bore to help unshroud the valve. The 6.0 can make awesome power with just a cam change and some long tubes. The cathedral based heads are a great unit wether they be 243 castings or 317s. I personally made 591 at the tire with a ls2 with a 239/243 @.050, magnuson 122 and kooks long tubes with a 1 7/8 primary. I would vote on the lq9 with a cam change and headers, unless you want to start playing with heads. You really can't go wrong with any of them, the LSX family is just awesome hands down.