Is it the exact same engine? Anything different? My friend wants to sell his for 150 to me, and it runs great. 104k on engine.

 

Not exactly.

The '84 has 2-piece rear main seal, all of the intake manifold mount bolts are at the same angle, good "old school" intake ports, and flat-tappet cam. '91 has 1-piece rear main seal, the center two intake manifold bolt holes on each side are at 72 degrees, the intake ports have a "swirl" wall built into them just above the valve (good for low power fuel economy and emissions, poor for upgrade performance), and a roller lifter cam.

The only things that would affect installing a '91 engine into an '84 car with the '84 car bolt-ons are the intake bolts and flexplate - but the '91 flexplate will bolt up to the '84 transmission.

 

Well he only wants 150 for it, could I mostly use it for parts?

 

What's the price of scrap iron these days? That's about what any 305 core is worth.

The '91 block is a slightly better part than the '84. As long as it is in serviceable condition, it could be argued that using that shortblock, with an upgrade cam, with your '84 heads and induction system, with appropriate exhaust and air cleaner upgrades, would be a good-running system. Other than that, there aren't any "parts" that are useable, and certainly nothing worth $150.

Of course, if the shortblock is serviceable, and your '84 bottom end needs rebuilding, $150 is a lot less than rebuilding your '84 shortblock would be. On the other hand, you could probably find a serviceable 350 shortblock for not much more than $150.

What's wrong with your '84 engine?