I'm partial to frybrid (
www.frybrid.com) mostly for the fact that they don't use copper, and it delivers more heat to the system. I pieced together a system pretty much identical to frybrid's and didn't really come out ahead...and had to do a bit of leg work. I'd recommend eliminating the headache and get a kit, whichever one you decide to go with.
If you go with the greasecar system in a colder climate, I'd suggest you add a heat exchanger right before the IP that is the first stop for the hot coolant coming out of the engine and the last stop for the fuel going into the engine (well, before the supply valve).
You could add a vegtherm, but I think coolant heat is more reliable and consistent than electric heat (and a by-product, so its re-using energy the engine is getting rid of anyway instead of taking energy away from the alternator).
Look over at the infopop, frybrid, and greasecar forums...there's more info (and more sympathy
over there).
Good luck,
-Geoff