I have a Zenith 601XL-B that's getting close to needing an engine, and since I'm out west in Southern California with family in CO, I'm thinking I need something with some high altitude performance and reliability behind it since I'll be flying over mountains - and of course I'm on a budget (10k?) which means I have to be a little more creative... I started off by considering: - 110-120 hp Corvair with super low time - a low time C-85 stroker with the O-200 crank and high compression pistons (which I've read can be good for about 105-110 hp) - Viking 130 BUT, then I discovered all these 912 mods out there, and now I'm also considering getting a used 912 UL, and modding it by doing any one of the following: 1 - A Zipper Big Bore kit w/ 1484cc (114hp) 2 - An Edge Performance 912 Turbo/EFI kit (up to 154 hp, but might be too pricey) 3 - A VZ Power 912 turbo kit - which look great and are supposed to be very affordable in addition to being DULV certified in Germany, and they claim 95 are flying reliably. I've emailed for a price list and am waiting to hear back. I like the Idea of a turbo with a variable pitch prop (and that new Kool variable pitch reversible and featherable prop for $2200 looks amazing). What would you do? Anyone here have any experience with any of these engine modifying companies, or the engines listed above with a Zenith 601/650? Thx!