I went looking for the how to buy a sled engine and what sled to buy it out of. That part seems straight forward. $6-7000 for a whole sled, pull engine, accessories, harness, sell the rest on ebay. If the redrive is under $3k it could be one of the best bang for the buck 100+hp packages out there under 200lbs all up. And that engine responds really well to boost.
Couldn't find any real info on this PSRU unit other than a nice installation video. Price and availability? The whole setup looks very well thought out although a sprag clutch only gives in one direction... overrun. What happens when the prop bites back wards. It works for helicopters but some of those have soft blade hubs that allow pre and post rotation.