White smoke and lifter noise

[BJarvis]

Little history on this pickup. 09 Silverado 5.3l automatic. Change out fuel injectors and was going through checking coil packs. Well my mother passed away unexpectedly and left me to pick up and deal with probate and everything then pickup started in with power reduced mode. Simple scan tool at parts store showed misfire cylinder 7. Replaced it all on number 7. Then it switched to cylinder 3 after clear.  Then backfired there throttle body. It pressured the number 3 cylinder with gas and stripped starter. Swapped intake manifold and all injectors, plugs, and plug wires. I hit it where it’s not loading cylinders with gas but thick white smoke while idiling. Should I just swap motors since I gave one out of a 07 Tahoe that ran when pulled or find the cause on pickup with 230k on it