I am a low experienced home mechanic. I have done brake jobs, intake manifold, injectors, head gasket, fuel pump, brake booster and master cylinder, power steering pump, shocks, belts, hvac, etc. Almost anything top side of the engine including knock sensors. I have never changed valves or lifters.

I own a 2004 Tahoe and 2007 Silverado (New Style) and a couple years ago the Tahoe engine blew a lifter that chewed up a cam lobe. It was leaking at main seal so I just paid to have a reman engine installed. I paid the $300 core charge to keep my original engine and 706 heads. It’s on a motor mount in my garage. It’s iron block.

I am now ready to start my first ever engine rebuild. It’s a bucket list item for me. My engine is a 5.3LT.
I ultimately want a 15 second car, 500 HP, etc but speed is not as important as a nice rumbly cam, headers, straight pipes, etc so it sounds really good and has some nice power for fun runs. Nothing serious.

I have no idea what I will put it into but my wife used to own a 1986 Firebird (non Trans Am) and was upset I made her sell it in 95. I think I will try to
find an old beat up firebird for it but will figure this out after I rebuild it.

I have 2 main questions.

First - that my 2007 Silverado has a 4.8L engine (iron block) and I was thinking about rebuilding the 5.3L as stock and put it into my Silverado as my work truck, then rebuild the 4.8 for my Firebird project. This gives me some needed experience before my fun motor project and avoids me losing my truck if that engine fails in near future. (Although I am open to getting another reman engine and having 2 engines to play). However would a 4.8 give me what I want (goal) in the Firebird, etc? Or would I regret not using the 5.3 later if I use the 4.8 for Firebird? My truck is running great and I have kept great care of it but it is 15 years old and 220K miles.

Second - I can watch a lot of YouTube for learning but wanted to ask for your personal feedback about what should I keep “as is” verses what must upgrade. For example are my pistons and piston rods ok to keep? Carb vs Injectors? Auto or Manual trans? I plan to buy a nice cam and new valves, springs, rods, and lifters.