[PeteLeathersac]

Looks like the balancer's too thin to be W31 but considering how all's been working out for you so far, it really wouldn't have been that surprising.
Still tough to read the stamped pad #'s from here, please note & relay them...is the 2'nd # a 9?
Exact applications aren't stamped like Chevy engine suffixes but the stamping there is the vehicle info and should be 9 digits beginning w/ a 3 for Olds division followed by year digit then plant digit ending w/ the sequential six of the original vehicle Vin.
Whatever the engine is, again you're lucky being an Olds that the crank's drilled for a pilot bushing so hopefully you can get it fired up and car moving around under its own steam to use while rebuilding the W31 engine.
Did you check the trans again and are there any more stamped #'s?
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete