easy way to change bolts that join y-pipe to manifold

Chrysler typically used regular bolts and nuts, not the miserable blind holes and studs GM and Ford used. Use an air cutoff tool to cut the bolts, then just lift the pieces out.

There's usually a stamped metal clip under the head of the bolt to prevent it from spinning on the assembly line. Those will crumble from rust, but they prevent you from getting a wrench on the head. Coat the new bolts with high-temperature anti-seize compound in case you have to take them apart again years from now.