Hmmm....sounds like the B&S cast iron I have in my '69 Gilson, with the PTO/driveshaft directly off the center of the flywheel. Similiar to the Cub 108 that I was looking at.
If it still has the carb on it, the B&S numbers are just to the bottom of where the air filter connects to the carb, on the same side of the flywheel cover as the carb. Left side of the shroud as you look at the flywheel. Should be a grouping of 3 number groups, stamped into the shroud. fine grit sandpaper or steel wool and a magnifying lens will bring them numbers right out. a good brite light helps, too.
As for parts, check at your local auto parts store, ie NAPA. they can get all the parts needed, as long as you have the B&S numbers that you can get off the B&S website. B&S also still supplies direct parts for these motors.
The local 'mower' people may not want to spend the time to hunt down old parts. But, they still exist. You just have to know where to look.