I found a truck listed as a 1968 f600 6x6 and I can't find any information on this type of conversion. I found marmon herring 4x4 conversions but none with tandem axles. Any ideas where I can get some information about this truck.

 

Do you have the vin code? could be a one off, have pictures? link to the listing if its on line? Any extra badges that are not on a normal truck?

 

It has to be a conversion (most likely by Marmon-Herrington), because Ford didn't offer an F600 with factory installed 4WD until 1971. Get the VIN and post it here.

 

I don't think there was ever an F-600 twin screw to put a conversion on. I have seen M&H conversions of F-750s. I spent a lot of hours in one when I worked on the Tras-Alaska Pipeline in 75 and 76. It was my field mechanic truck. I think an F750 could have been ordered as a twin screw but was the smallest F series with it available. But the I could be wrong.