There is no doubt the Moki 215/250 is the premiere engine of choice for this plane, but keep in mind the new DA120 (or equivalant) can be used for power at MUCH lower cost.
With the DA, some compromises will have to be made, but no one should deny themself the fun of having the most bad ass Thunderbolt on the block just because they lack the bank for a big radial...
I am still waiting for Dave at Desert Aircraft to ship me a 120 so it can be illustrated in the Builder's Manual.