I have some experience with the 3959512, which this appears to be. You can see some more info in this thread and the links within there.
https://www.yenko.net/ubbthreads/ubbt...day-2-dyno-day
Though it has the road draft holes, it should be a medium journal crank (typical 350 size- bigger than small journal 327 but smaller than the 400 sbc mains).
I think this block showed up in 1968 and wax mostly used in CE applications.