Last year of the HG68

[Kirk-NJ]

I just picked up an HG68. The engine is an IXB-3 Production code 5-2-51 but I think the engine may be a transplant because there is a tag on the frame with I can't read because it's covered with some steel to brace a hydraulic pump. My question is when did they stop making the 68 or was it used until the end on the run in '51 or what was the last year? If I can fingure out how to add photos I will.

Thanks, Kirk