Need a GM 5.3L replacement engine, who do you recommend?

unfortunately 2005 was the first year in the trailblazer and envoy with the 5.3 2007 the tahoe i think truck followed after . Terrible design

 

Ehh, not a bad design at all. Ninety percent of failures are from cheap oil/ poor service history. From what I’ve seen anyway.
It’s actually the best design engine out there for that generation of car and trucks. Simple, effective and pretty much bulletproof.
Unlike the Dodge that eats cams because the cam is too high in the block and doesn’t get enough oil.
Of the crap ford is throwing out there, hell there ain’t nothing good about that shit.

 

I don’t know. My ‘06 non-AFM, 5.3L ate a couple lobes and the corresponding lifters at 99K miles, with Wix filters and full-syn every 3K miles. I think, it’s hit or miss.