If you change pistons, it really should be re-balanced. And new rod bolts and resizing the rods is also a very good idea. There goes a few hundred dollars.

How far out of spec are the cylinder bores? Keeping in mind that the budget is the prime motivator, why not just re-ring it?

If the cylinders aren't a train wreck, you might think about a hone job and throwing some new rings in along with new bearings and calling it good.

Way back when, we used to do that all the time. I remember knurling pistons that were way out of spec for the cylinders. It worked well in low speed applications. You can get several years out of a cheapy job like that if the pistons don't flop around in the cylinders too much. And of course, they make rings just for this.

It might be best to either do a full-on economy assembly or a full-on re-build. Not something in between.