1990 4.3 fit in a 1999 blazer

[68c50]

Im looking at buying a 1990 c1500 with the 4.3. I'm just gonna use the trans and axle for my truck. My mom has a blazer with a badly knocking 4.3 vortec. My question is would the older engine work in her blazer? I know we'd have to use the 99 intake and possibly heads. Would anything else need to be changed? She's not looking to put alot of money into it as she is trying to sell it. Any advice would be greatly appreciated.