Model?
 

How would one figure out the model of an IHcub without the decals? I have two believed to be of years 1968 and 1972

Do you have a picture of them?

A 1968 year would be a model 72 or a 1x4 or 1x5 model.the 4s are gear driven, the 5s are hydrostatic.
The 1972 year would be a model 86 or 1x8 or a 1x9 model. The 8s are gear driven and the 9s are hydrostatic. Pictures would be helpful.

So would serial numbers.

Where are the serial numbers located? I am working on the older one and haven't seen a tag on the frame as of yet. Bother are gear driven with a "hi - lo" pre-drive

It should be on the bottom left corner of the transmission.

S/N locations....
http://cubfaq.com/serialnumbers.html

Found a number in the casting for the transmission "385058R1"
Can't figure out how to add a picture

That looks like a casting#. The serial # should be on a tag on the back of the rear end. Should be mounted to the left of the rear cover.

Could be stamped into the reduction housing on a square boss or into the rough casting itself like the originals.
Really small numbers, may be painted over and hard to read.
If on a tag left rear side of the differential housing, and the tag is missing, there should be evidence of the holes or maybe the rivets will still be there