I agree a Merlin vt 80 on that airframe would be great, amts are great but very heavy a p80 will shed some weight but not a ton it's still a big engine..the latest generation 80 and 100n turbines on that airplane would be the ticket...not to mention much less thirsty than an old p80 or mercury. The AMT is not the most efficient engine, and remember the only way to get more power is more fuel keep that in mind on an airplane that doesn't carry very much of it..I don't remember how much my razor carried but I believe it was only 70 some odd ounces.
As mentioned earlier though unless your a total speed demon most of your flying will be around half throttle on that slick airframe...have fun with it, it's a good one.