Let me ask the obvious question - why the rebuild? Is the bike running now? Before you sink money and time and risk possible additional issues associated with boring cylinders etc., have you confirmed compression etc. in the cylinders? You might not need a full rebuild.
For the $120, you get a fantastic deal for new pistons, rings, pins, circlips and a head gasket. Cheap at twice the price. Boring/honing the cylinders would run $30 or so for each hole. If you do the wrenching yourself, that should be the total cost.
Of course, while you have your cylinder head off, it's a good time to get the valves reseated and replace the valve seals, and perhaps whatever guides need to be replaced as well. Could be another $200 or more depending on the new parts needed.
So you're looking at $240 - $440 or so for the top end rebuild + labour. These bikes can quickly eat up even the most substantial of budgets. Either stick to your budget and spend the money where you need to only, or don't pay attention to the total spend. Many of us have spent more on our 30 year old Hondas than it would have cost to buy a much newer bike in decent condition.
I for one don't regret a penny of the money I've spent so far, even though I could have bought a decent running 70's/80's BMW at this point for the money.
BTW - I too have spent time in New Mexico. Funny how it draws people in. I lived in Window Rock Arizona for a few months back in the early 90's, and spent considerable time in Cuba, Gallup, Albuquerque and Santa Fe.
