What to do with it?

Decisions - decisions ! Don't fret over it !

Look at the post from 340sfastback. That's the way to go. You can use stock low CR cast pistons and do it cheap if you want.

For what its worth - Ive been finding that most of the later 318's that had moly rings in them when new, have almost ZERO wear in the bores. A motor my son and I picked up for free (an 87 or 88 318 roller block) had no more than .001 to .0015 wear in all the bores, checked at three points on the thrust and non thrust surfaces. That's darn good, it means you can use stock standard size pistons. We also built another late 318 that had similar wear = zero.

I'd pick your best block after measuring it out, hopefully you'll have luck like us. Hot tank the block, new cam bearings, freeze plugs, a quick hone job, and balance the mess together.

Run some # 302 heads on it after bowl porting and 1.60 1.88 valves, or put some 360 heads on and run it.

My .02 !

Have Fun deciding !