I noticed that a GMC truck oil pressure gauge has the range of 0 to 60# does that mean that GMC engines were insert bearing engines rather than babbitt oil slingers?

That is correct. My 36 GMC has insert bearings and a 0-80 psi gauge, however mine runs in the 20 to 40 psi range.

GMC used a variety of of GM enigines. Up to 1933 the 1/2 ton used the Pontiac 6 cyl. engine in the small trucks. Large trucks had versions of various 6 and 8 cyl. Buick engins.
In 1934 they used the flat head 6 cyl. Oldmobile engine in the small trucks. This continued through 1938. In 1939 they came out with their own valve-in head straight 6. Itused a few odd chevrolet parts.
All of the above mentioned engines had full pressure oiling and by about 1933 went to rod bearing inserts.
Chevrolet went with the splash oiling in trucks through 1953. Rod inserts and full pressure came in 1954.
By mid 1920 all GM engines had full pressure oiling except Chevrolet.

If any of the above is in error one of our new GMC members can correct me.

Have gotten the motor # A228 302 731 from the engine and have determined that the size of the truck is 228cu. The motor casting GMC - 5 # 6107326 which I think makes this engine a 1952. The cab # is 253 22 S 25.. which I think means it is a one ton vehicle. Does any of this make sense? Can anyone provide any more information or correct my research errors.

A 253-22 is a 137" wheelbase 253 is a 1 ton from the info. I have.

Actually I think the '39 and later GMC 6 cyln engines used very few Chevrolet parts. It is my understanding that the GMC engine is quite similar to the Buick in-line's. All of the GMC OHV 6's had insert bearings, rods and mains.
I know the water pumps from some Chevy 216's will fit the GMC's as will the bell-housings.
When I put a GMC 270 in my '38 Chevy in 1951 I used a '39 Chevy water pump, it was shorter than the GMC pump, and the '38 Chevy bell-housing. The three speed Chevy trans spline fit perfectly.
I used the stock Chevy oil pressure gauge. The minute I hit the starter the needle went out of sight, (80lb's on 30lb) The needle came back into sight when the engine was turned off..

Thats correct, only minor parts were shared with Chevrolet.
By the way, a Buick didn't have rod inserts until 1948.

I always found it to be quite odd that Buick stayed with the babbit bearing for so long, of course the Buick's were not well known for having rod bearing problems like the Chevy "stove bolt sixes".

Not exactly but close enough. '38 light duty GMCs used a Pontiac flathead. The 228-236-248-270-302 inline six gasoline engines are all the same size block and why they are easily interchanged among models. 39-62 was the production window for that size block, though 60-62 the 302 only for military. Post '52 military blocks were sealed engines to run on a snorkle so they are the same size but set up differently and need modifications to use in civilian GMC truck applications.

http://www.oldgmctrucks.com/photos/EngineSpecs_Pg1G.gif
A indicates the size of the cylinder, rod, and, crank journals which in this case is + 5 thousandths on cylinder bore and - 10 thousandths on the crank and rod journals.
228 indicates the engine size
302731 is the regular sequential production number of the engine

Hello guys! I just joined the forum.

I have a 1954 GMC with a 248. Im currently having the engine rebuilt and and am curious to know what engine parts can work with both the 228 and 248. This will help me source these rare parts. My first question is the oil pump? Did the 228 and 248 use the same size oil pump?

Most listings for parts, whether in a paper catalog or online, will list all of the applications for a given part. I don't think you will have to do your own interchange investigation.
There is a forum called Old GMC Trucks where they speak only GMC. It would be a good resource for you. Good Luck with your project.

Mike