99silverado4.8

Hey my names matt I have a 99 Silverado 4.8 I know its not the actually ls1 but I've heard its part of the Ls family so I figured I could learn about some good mods I can do to make it quick I eventually want to swap a lm7 5.3 but it'll be fun to build my 4.8 just to see what kind of numbers I can make I have 2 4.8 motors I have 2 sets of 862 heads I've read that valves an springs along with porting an polishing they are a decent head so if anyone has any info on that I am open to suggestions one set has 186xxx on them an the others have about 123xxx are they worth building? Also if anyone has any info on putting around 8-10 psi I know I'll need low compression pistions would 5.3 piston heads work with 4.8 connection rods or would that just be asking for trouble thanks glad to be apart of this page