I've used boring machine bits in my Hole-Hawg. It's tense, to say the least.
Lotsa torque, and it doesn't stop as soon as you let off the trigger. There is a brand of bit available called Wood Owl. They only go up to 1.5", but work very well both in electric drills and boring machines. You can buy a wooden framed boring machine in good shape for about $200-$250, when you are ready. The advantage of the boring machine is that it keeps the bit perpendicular to the timber, and also controls the depth. If you are steady with your gas drill, you can get by with that, however.
Square rule joinery accommodates differences in timbers. Using a 7.5" "ideal" timber will allow your 8"x8" timbers to be as small as 7.5" and most any width over 8". Most mills will keep you in a +/- of 1/4", which is fine for this type of joinery. The tighter your joints are, the better the frame will look. Even a very tight frame will look a little loose after the timbers dry, especially if it's a heated building, that's just the nature of the material. I like it, myself. I'll dig up some pictures of some of the stuff I did in the cruck/scribe workshop later. You can join most any two pieces of wood, once you know how.
If you don't feel like tackling the initial tune-up of your tools, contact Jim_Rogers over at the Forestry Forum. His tool partner does all of the initial work on the chisels he sells, and he does a very good job. They will do this for your chisels, but you'll have to ask what it will cost. It can take a bit of time to take flea-market tools up to working condition. That's why Jim gets $80-$100 for his chisels.