Back fire and power loss

For 1987 I assume that you may have a carburetor. Sometimes a backfire will ruin the power valve diaphram. Not a real expensive part and not too difficult to change.

Thanks will dig deeper

Hook it up to a diagnostic machine for the correct answer. Too many things that could cause a backfire. And, we don't know if it's backfiring through the carb or exhaust. Those engines were notorious for cracked exhaust manifolds so check that. Backfires are caused by raw fuel getting into the exhaust system before igniting. So, suspect the timing off, plug wires, wrong carb settings, timing off, cracked rotor cap, etc. etc. etc....Dennis

backfire thru carb or exhaust. If exhaust then the spark stuff.

Why plug wires? Could be cross firing between cylinders.

This is a long shot but do you have a vacuum hose unhooked somewhere?

Backfire through the exhaust is too rich, through the carburetor is too lean.
Although if the firing order was messed up or a plug wire was damaged that could be the issue.

Plug wires is a good bet!
Verify firing order
I didn't see a new distributor cap.

Timing?

Spark plug wires???