Bolting a balancer solid without the rubber damper ring probably wouldn't be a good idea. The reason the ring is there is to absorb, and then oppose torsional twisting of the crankshaft every time a cylinder fires. Inline sixes are pretty forgiving so far as balancing goes, because each connecting rod journal is 60 degrees of crankshaft rotation away from the next one. When spinning an I-6 crankshaft up on a balancing machine, it's not even necessary to use "bob weights" to simulate the weight of the pistons and connecting rods. Try that with a V8 crank and it will jump right out of the machine.
Now, before some self-appointed engine guru chimes in, dampening torsional vibration is different than balancing a crankshaft. That's where the damper comers in. If an engine is going to be used for pulling heavy loads at or near full throttle and high RPM, having exactly the right damper in very good condition is much more critical than on an engine that's driven at moderate speeds and loads. So far, I haven't heard of any catastrophic failures of the 2-groove dampers I've been putting together from new V-8 parts, and they're being used on several 235's. Something similar can probably be fabricated for a GMC, since the hub diameter, inside and outside, is the same as Chevy sixes, and the balancers will interchange, I believe.
Now I'll retreat to my foxhole, put on my steel helmet, and duck and cover from the incoming ridicule in 3-- - - -2- - - - -1- - - - -!
Jerry
