The stock Vortec 7400 heads are net lash- to do much w/them the first thing that would be needed is to swap out the studs and lock nuts for adjustable ones.
Both Vortec 7400 heads (the '98-'01 12560241 and the '96-'01 10141279) are about 100cc, as a comparison. As you can see HERE
, much care has to be used if porting these heads, they have a "peanut port" sized intake port w/a vane cast into the port as well.
The 049's (113cc-plus chambers) would flow well, except the Gen 6 has basically a FT piston, and that will kill the CR w/the open chamber heads. The 390's have smaller chambers (about the same as the L-29 heads) and so would be about the best compromise, IMO.