Looking for a service manual for a 112 2M487SP, but all I can find are 112 91G1-UP & 46D1-UP. Just wondering if most of the information would be the same or not?

Your right, I could not find one listed for the 2M.
The 91G1-up is a model 112E w/D330 engine of 1965-69 vintage.
The 46D1-up is a model 112F w/D330T engine of 1965-68 vintage.

The 2M will have the D4400 engine which should not be a problem to find a service manual for. I guess you will have to rely on the parts and owners manual for the rest. Can't say if the 2M service manual ever existed or may just be out of print.

There is a Servicemans Reference Book for the 2M series, Model 112 .. but it is extremely rare. It appears that SRB's for the Cat 12, 112 and 212 were not produced until mid-WW2.
You may get lucky, and find a military TM-5 manual for the 2M series Model 112 from WW2.
These were put together using the Cat Service Manual, the Operator Manual, and the Parts Book, in the early part of WW2 .. then later, the TM-5's were re-written by the Military, and the end result is usually a better manual than the Cat original.

I have a number of cards with Caterpillar "lists of publications" from the late 1930's to the early 1940's, and the last one I have, dated March 1942, shows under "Road Machinery", only Service Manuals for the #7, #9, #10 and #11 Auto Patrols .. but nothing by way of Service Manuals for the 12, 112 or 212. I do have SRB's for the Cat 12 dating from late in WW2.

The early Service Manuals for the graders covered both engine and chassis repairs. It wasn't until the early 1950's, that the SRB's for the graders were split into chassis SRB's and engine SRB's.

The Cat list of Legendary Literature also does not show any availability of an early SRB, or SM, for the 2M series 112.

www.cat.com/cda/files/268568/7/motro_graders.pdf

I think I may be a bit slow, can't seem to figure out what that web site is supposed to tell me. I see the 112 S/N 2M1 - 2M814 but don't know what to do with this info. from here?

That list is a file download from the Cat.com site, which lists all the publications that Cat will reprint for you, under the "Legendary Literature" publication reprint program. The important # is the Media #, which is called the "Form Number" on the original manuals and books.
You can print out the relevant page or pages from that file - and then go see or call your Cat dealer parts man to order any of the Legendary Literature reprints .. or you can order online ..

www.cat.com/cda/components/fullArticle?m=90800&x=7&id=268698

Hi catcrazy,
Probably the most important column of information on the literature website is where it identifies what the document is......along with the various serial numbers. Takes a little getting used to the codes:
PM....Parts Manual
PC....Parts Catalog
SM....Service Manual
SR.....Service Repair
IT.....Installation instructions
OM...Owners Manual
Other special applications I didn't cover:)

Also watch for the latest in printing versions and end of series publications
Also watch the language column which is pretty self explanatory.

It certainly would help if they published a glossary of terms and abbreviations but such is what we get.