This is a question of whether you are doing a full repair or just getting it running again. The fit of the piston skirt is one of the critical aspects of making the engine durable and quiet. If your piston is missing a chunk of skirt, it is quite likely to be cracked and mishapen. You are spending money on this project - it probably won't cost much more to make it a reliable job.
We've all done less-than perfect repairs on old machines to save money, but they have to be capable of working. I once "fixed" a set of worn-out car pistons by widening the top ring grooves on a lathe and putting steel rail rings beside the new compression rings as spacers. The original ring grooves had worn out of square, and this was a way to fix that - the car was unusual enough for a new set of original pistons to be expensive. Even so, I wouldn't have done it if I'd been trying to make it into a good-as-new car; I figured it would be commensurate with the condition of the rest of the car. It was successful as far as it went: I drove it 30,000 miles and sold it in good condition.
