Interesting, I was looking for a new torque wrench just yesterday. I had also decided that my next one would be a split beam model, and similarly, my needs are in the 70-80 ft-lb range (for lug nuts).
The 3/8" Precision Instruments model is a little less expensive than the 1/2" and goes up to 100 ft-lbs, which would work for us.
I have no doubt the 1/2" model (22") would work, but my old spring type 1/2" torque wrench (20") was occasionally longer than I needed (bumping into bodywork while torquing), and thus a little unwieldy. The 3/8" is almost perfect at 17" long, except for the 3/8" drive over the 1/2" drive, which a simple adapter would fix. However, I would get the flex ratchet head if I were to get the 1/2" split beam model, so the size may not be an issue.