pbf engine.
Go with a light weight engine because you want the CG back. I have a Norvel Big Mig 25 on mine, my brother has an OS 25 FX on his. I like the OS much better and I will not buy another Norvel. The OS always starts in a couple of flips and I usually need a starter on my Norvel. With the OS, all you need is fuel and a glow battery. Anyway, that is my .02.....
Dale