Install a new engine? help!

Hello, I'm new to this forum, so please excuse me if I'm not in the proper place

I'm trying to help my 77 yr old dad. He's putting a new engine in his old truck, with the help of 2 of my sons.

It's a 5.7L, 260 hp, 350 cubic inch. It's already in the truck, but not all 'hooked up'.

Looking at the old engine, he noticed 3 holes that are plugged, but in the new engine, the holes are not plugged.  They are around and above the crankshaft boss, in the rear of engine, and they go into the block. He's not sure of the size, but says that they might be one quarter inch pipe, or threaded size. What are they for? And will oil they leak oil if not plugged?

I am hoping to save him pulling the engine back out again if he doesn't have to. My sons can only help him on the weekends, and I sure don't want him pulling this back out on his own.

If anyone can help, I would surely appreciate it!
Thanks!  

Sounds like the oil galley plugs if so they will leak.
John  

Yep, definitely has to be the galley plugs. Gotta have those sealed or you'll have a disaster on your hands. Odd they weren't installed on the motor, they're included with any freeze plug kit for a small block Chevy.