ORIGINAL: low@slow
The general rule of thunb for 4 strokes is .1 cubic inch per pound. If you are going to end up with a 12 pound plane, a 120 would be a better choice. Remember that you will need to run an 8 pitch prop for the airplane to go fast enough to fly right. If it was me, I would get the plane basically assembled and do a CG check. If you are tail heavy as probably you will be, a big heavy motor works better than adding weight.
Gotta say that I totally agree with the 'general' rule of .1 cu. in. per lb (except with Y.S., as they have MUCH more power per cu. in.).
That is why the Saito .82 is a good choice for current Top Flite Corsair project, which I anticipate weighing about 8.5 lbs.
I don't agree with the 8" pitch tho: I prefer bigger props with less pitch, some down to 6" (pitch), and I can assure you, mine fly right