Okay, I might be getting my grandpa's old 89 sierra. I think it is the 4.3 v6. How good are these motors, and what should I expect to go bad, being that old.

Intake gasket leak is the main thing I know of.

i have a 89 sierra 4.3 liter ... just in the last couple of months have i started driving it full time problems so for - back up lights ( circut boards were so rusted they had to be replaced , thremostat , the radio (output went out) , muffler and tail pipe , sparkplugs and wires , distributer , im am now just dicovering the possiblility of a blown intake manifold gasket and thats probly what it is im constantly lossing coolant and i can find no leaking and my temp guage is going wacko cause of it .