I replaced a balancer on my 250 while in the truck ( '37 ). It was tight fit, pretty ssure I had the radiator out of the way. The old one pulled off with a balancer removal tool. The new was placed in an oven and heated to 200 degrees while the truck sat outside for a hour or so in 20 degree temps. While the truck was still in the cold, I had on heavy gloves, grabbed the balancer out of the oven and made a run for the truck. In one quick motion I shoved the balancer on the crank and made it about 80% or more onto the crank before it got stuck. A wood block and hammer seated it fairly quick before cooling completely.
The bolt is nothing but a stop, it doesn't hold the balancer to crank, the press fit and key do that. The washer and bolt just keep it from coming forward. The added bonus is you can use the threaded hole for installing. Pontiac's use a 5/8-18 bolt torqued to 160ft lbs, they will stilll crack the keyway if the press fit is not tight.
If you use the hole for installing the balancer, insert a stud into the crank and use a nut, washer, and oil to push the balancer on. This puts all the force on the nut and external threads. The stud will have the full length of internal threads to hold on to, if you use a bolt you are pulling a lot on just a few threads while starting the install.
