Tractor and Engine ID

[Mark]

As was described in the post about steering clutch lining, I was recently was given what I believe is an OC-3 Cletrac.  It has a replacement engine currently installed and I also have the original engine.  Can anyone tell me a little bit more about what I have from numbers I have been able to find on the tractor.  I would be especially interested in a date of manufacture.

The bell housing is marked: OC3 - 42
                                      16WH - 372

The original engine is marked on a tag on the side of block:  
                                   IXK3   3 1/4 x 4
                                    125735

The replacement engine is marked IXB3    
it also has a six digit number I can not quite make out.

Thanks for your help

[walter hudson]

You have a 1956 model oc3 68 guage. The only difference in the IXB and IXK is the bore .
Walter

[Mark]

Thanks Walter