[North Coast Cab]

Fix the motor you have. PU a decent head and do the belts and be done with it.
Replacing it with a motor that is unknown and thus susceptable to the same issue is not a great idea.
That said if you did decide to swap it I have a few comments. The later the motor the better, period. There are lots of little changes and improvements in the motors every year. The very early motors have different crank oil passages, a less aggressive cam, and less oil pan baffling. Yes they have forged rods which is nice, but at 100k miles they need rehabed too. The automatic tensioner comes into play in late '87 and is a plus. The early motors have different wiring harnesses as well as a different AFM and DME. You can swap these all out if with the motor. The only issue to watch is the '88 not only has higher compression pistons, but it has some different tuning in the DME.

Good luck. Unfortunatly you are about to put as much into the car as it is worth.