So there are two ports next to eachother right above the dip stick on my 70's model sbc 350. one is for an oil temp sender, any idea what the other one is for? the oil temp one is directly above the dipstick, the other one is towards the front of the block a little bit. Also does anyone know the exact size and thread count for these holes? i am trying to get two plugs to block them off so i can finally start this thing!

If you have a can of spare bolts, find one that will fit, then get a plug the same thread. A cheap thread set of thread keys, kinda like feeler guages with all the thread sizes, comes in handy.

Typically, holes in the side of the block are pipe thread. Usually 1/4 or 3/8 pipe. If it's really small and looks like fine thread it is 1/8. Typically on each side of the block there are coolant drain plugs, might be that. I'm not familiar with Chevys so you'll have to figure out what is what.
Travis..