Leave the stock main bolts. No gains, not even piece of mind.
What are the dimensions/measurements and dish of the Pistons that are in it now?
9:1 compression or close would be fine for that setup and run pump gas.
Only reason to put new Pistons would be for compression change. Measure what you have and see if thin head gaskets and mild head milling would get you near 9:1.
I'd be shooting for $400-500 in putting that long block back together.
