There are PLENTY of lighter pistons on the market for 440s. Just google it or cruise any mail order website. There are good, honest vendors here on the sponsor page as well.

Same with rods. I'd stay away from super cheap eBay rods, but there are plenty of offerings in
the aftermarket that makes re-doing 40 year old rods a waste of money for the risk involved.

Enjoy the project with your sons. That in itself is awesome!!!