Barry, yes you can get the ZDZ engines from Chief or direct from Cactus Aviation.
ZDZ also makes a rear exhaust 40cc that lets you keep everything inside the cowl. I think the gas engine made a little more power than the Saito but again the reason I changed it out was the frustration of trying to keep the big Saito from flooding on this plane. I'm sure there are things I could've done to correct the problem, but at the time it just seemed quicker and easier to change the engine out than trying to move the fuel tank or mess with pumps and regulators. Having said that, I think your going to be very impressed with the 160's power on this plane and I haven't heard of anyone having the flooding problem with the 160.