RE: Engine for 4 Star
I'm with Rich. If you are concerned about the cost, the most bang for the buck seems to be the Tower .75. I personally don't have one, but there are 2 at my field and the owenrs love them. One is in a little 40-sized CAP and it gets hot rodded around a lot.
The Tower is well supported by Hobby Services and parts are checp and, as I recall, go postage free.