Peter,
Yes, if I were to make the decision right now... it would be IO-390.
Go to Dan Checkoway's site and do some W&B scenarios. The airframe, in my mind is more suited for the heavier nose. Dan says so in his info too.
My reasons are:
1) Well, I am a self admitted power junkie
2) Weight and balance is favorable (can still have 100 lbs baggage too!)
3) Wheel landings are easier (and preferable in an RV according to most)
* I see you are a nosedragger... this is good for you too
4) Heat is unlikely to be a factor because it is mild compression
5) Similar to #4, with low compression it is likely to be less troublesome (TBO, MoGas, cooler etc.)
The trick isn't the block. It is the jugs. There is no replacement for displacement!
I like big jugs!

CJ