I know this is a diesel website and I do have an 11 LML. I also own a chevy colorado with a 5.3 V8. I was thinking of porting the heads changing the valves, and putting a C5 Z06 cam in it, any ideas what kind of HP gain I will get, and think the stock Tranny will hold up? Thanks

Yes the tranny will hold up. You will gain 20hp with cam,headwork a bit more, then u need valve springs,and tuning. I did cam,springs, ported tb, kooks longtube headers 1 7/8",cai,underdrive pulley and 160* stat on my 03 Z06 and gained about 70-80rwhp, it makes 420 rwhp on a mustang dyno. If i did it again i'd go S/C. Google pat G. He does good tuning and cam selection and he's in TX. Good luck.