Good news- - - - -you found the problem! That balancer just didn't look right when we were running the engine in the shop. I'd suggest a drill and tap job to keep the new balancer in place even if the press fit on the crankshaft snout has gotten a bit loose, and a healthy dose of green LocTite on the crank snout as you install the replacement balancer. Unless thr keyway in the crankshaft is really sloppy, the LocTite will stabilize the key, also. Also, by threading the crankshaft, you can use a balancer installer instead of hammering the new one on. I've got the necessary tooling to do the job, if you need a little help with the drill/tap/install process. The same bolt and washer that is used on a small block V-8 can be used on the stovebolt engine with a little tinkering.

Call Jackie at Internal Engine Parts Warehouse on Foster Avenue to see if a new or reconditioned balancer is still available for the 235 engine. Good luck, and keep in touch!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!