Thanks for the welcome guys.
I have been in touch with Arias pistons and without sending in my exact requirements they said it would be around $160 USD per piston with a minimum order of 4, discounts for more. That is not bad at all, and I think I may be pursuing this as an option. After reading through Michael’s big bore thread I found the link to LA sleeves, which could be a relatively cheap way to get a new set of sleeves. Hopefully I will have some time in the next month or so to break down the junk motor I have and get some measurements to get a firm quote on the pistons.
This very well could be a pipe dream, but after reading about people re-phasing their XS650’s I’m wondering how insane I would be to attempt to try it. The 750 has a single piece crank so a custom pressed crank would probably be necessary to facilitate this along with re-phased cam and ignition. At the very least I’m going to have the crank lightened and balanced, but a guy can dream can’t he?