12 bolt rear diff?

[68chevystepside]

I have a 68 c-10 stepside that originally had a 250 straight 6. I am going to be installing a 350 out of a 89 g30 and a t400 trans out of a 90 chevy truck. I counted the bolts on the cover and it has 12. Will my original rear diff be able to handle the v8 or am I better off trying to find a different diff assembly. Or can I upgrade the internals of the diff. I plan to just have a few performance bolt ons and that's about it.