Tom, what are your goals here? OEM M-code 351-C in Panteras were redlined at 5900/6000; that's about all the cam, stock hydraulic lifters and OEM valves could reliably deliver under load. For under 6K max revs, about any balancer will work. It's when we push the revs to 6500, 7000 or beyond, that Plan A needs modification.
The near-stock 351-C needs a 28.2 inch-ounce balance factor on both the harmonic balancer and flywheel to work correctly. 50 inch-oz balance factors were used starting in the '80s after Clevelands were out of production. If used, 50 inch-oz on either end of a crank will quickly tear a near-stock engine apart, sometimes breaking the crank or motor mounts.
Some references say OEM Ford balancers were bonded, some say they were only press-fitted and some say the Boss & HO series was both. The outer ring on old assemblies has been known to get so loose that it spins off and hits the pavement or walks back and wears a hole in the oil pan. A few balancer rebuilders use RTV to glue the two iron parts together and I doubt anyone knows what the real vibration-absorbtion effect is with that technique.
I believe the most important thing for you is, your balancer of choice should be new since rubber deterioration with age (and oil leaks) is the killer here. Not expensive at all.