It should fit and you should probably use the tranny that came with the 5.3, it would make life a lot simplier as you have to use the computer from that engine and it regulates the tranny also, on top of that you will have the advantage of a good ove...
It depends on what you're buying! I'd take a 1969 Dodge Charger over a 1980 Chevy Citation.......But I'd take a 1956 Chevy Corvette over a 1990 Dodge Intreped.
I suspect you may need to replace the distributor with an older HEI unit. I THINK yours is controlled by the computer on 1990 vehicles. Check it out.