Another scrap yard treasure

Scrap man called about a CAT engine that came in the yard. This is what I found. I bought the engine, D4400 1S3179SP. Being a trencher, it has nice rails and pads, but an ODD size. If anyone know what they might fit, let me know. Pitch is 6 9/16" inside rail is 2 1/2", outside of rail is 5 1/2". Pad mounting is 4" X 4 1/2" and 2 1/4 " apart with 1/2" bolts. The pads have "Allis Chalmers" on them. Forgot to measure the width. Rail casting # is 67 3500?2.
The # before the 2 could be a 1.

hello Eds-oldiron,the best i can come up with is hd6.
hd6 =6.50'' 165.1mm , if my calulation are rigth ,bruce oz

Pitch is 6 9/16"=165.1 mm????????
serial number ,best i can do is ,1s3179sp is from 1942-47

Thanks Bruce... I just took a look at an HD6 down the road from me. The pitch on it is about 6.500 which would match what is on the trencher, but that is where the similarity ends. The inside width on the HD6 is about 3" and 5" on the outside width. It also has rectangular pattern for the pad bolts. My thought was if these trencher rails fit something useful, I would buy them also. They are going to cut it up tomarrow. I will pick up the engine and transmission this weekend. Souldn't take much to get it running.