GM Engine Casting Numbers????

I have what I believe is a 350 Engine. Can't find any info on it. Just wondering if someone could help me. The casting numbers are:

Block--1382201
Head--1237650
Intake--B1238402
Exhaust--1236336

Looking to put this engine into a 1968 GMC 1/2 ton pickup.

As this is the "Pontiac" board, do you mean you believe you have a 350 Pontiac? A Pontiac is easy enough to identify. The timing cover is aluminum and has the water pump bolted to the front, similar to Fords and small Dodges. The exhaust ports protrude from the head. The casting number on the center exhaust ports is what is used to identify the heads. The block should have the displacement cast into the side, near the front freeze plug on the driver's side. There will be a 2-letter code stamped (not cast) into a pad machined on the passenger's side front of the block. The date code is in the back, next to the distributor. It will be a 4-digit alpha-numeric code.
While there are books containing the numbers you identified, few shops will have them. I have described the "every day" method we use to identify a Pontiac. Those books are available through AERA (Automotive Engine Rebuilder's Association) or PERA (Production Engine Rebuilder's Association).