1. As said, if the RPM is not increased, you don't need stiffer valve springs, which means you also don't need different retainers. (assumes the existing valve springs are not defective.)
2. Are you sure those retainers are compatible with those valve springs? I didn't research compatibility.
3. Yeah, Vortec heads crack.
4. Yeah, valves and valve guides wear out. You do anything to the guides--new guides, new guide liners, knurl the guides, or ream the guides for oversize stems, you'll be cutting the seats, too.
5. WHAT lapping compound are you going to use? Permatex lapping compound--the grease type or the water-based type, both sold at typical auto-parts stores--are so coarse you might as well get some sand out of a kid's sandbox. I use "Clover" lapping compound, 400 grit--and I probably should have bought 600 or finer.
6. I verify valve face-to-valve seat sealing with a vacuum tester. Most folks won't have access to that equipment, though. Depending on wear to the valve faces and valve seats, lapping may not produce a proper seal. You may need the faces and seats cut/ground.
7. Are those valve stem seals compatible with your valve guides? Last set of valve seals I installed--on aftermarket heads, not Vortecs--were Viton, not metal-bodied, and didn't need the guides cut down to fit.
8. Are Vortec head bolts Torque-To-Yield (TTY)? I didn't know that. I assumed they were plain ol' ordinary reusable bolts.
9. How thick are those head gaskets? My TBI 5.7L had the pistons .025--.028 in the hole. A .015 thick head gasket would have been plenty thick. Stock was, I think .028 thick. Makes for lazy combustion due to lack of quench/squish. I bet that gasket is .040, which will be even worse. I had my block zero-decked, and then used a Summit-branded head gasket at .039 thick.
10. You have the timing cover off? Is the damper grooved where the seal rides? (almost certainly is.) You'll want a repair sleeve to cover the groove. About $7, easy to install. I've used Fel-Pro and Timken repair sleeves most recently, but there are other suppliers. They all go on about the same way. Start 'em straight and use a block of wood between the hammer and the sleeve. They'll come with some red sealant, apply to the outside of the damper at the leading edge. Don't forget to re-seal the damper and keyway when you press it back onto the crank snout. The Vortec plastic timing cover is supposedly one-use-only, but I'd consider changing the seal, and adding some sealant to the "gasket area" of the cover, and slapping it right back in place. Never actually done that, though.
11. For those of you changing rocker arms, be aware that you need either self-aligning (self-guiding) rockers, or regular rockers plus guideplates plus screw-in rocker studs plus HARDENED pushrods. Self-guiding rockers are the easy solution.
