The 3970010 casting number was used for 1968 327 engines and from 1969-1979 on the 350 in virtually every configuration of 2 and 4 bolt build imaginable.

I would not mess with the bearing(s) unless you suspect a problem. Is the engine making a knocking noise in the lower end? While it is relatively easy to change bearings with the engine removed from a vehicle, it’s not just a simple “slap-it-in” procedure while lying under the truck as there is a certain level of measuring and prep work required to make sure the bearing fitment is correct.