I made one for my 126 and it looks nice. I used the hitch for the 300td and with a lot of cutting - welding it works. There are drawings and an explanation of how I did it on here somewhere just look. The 126 did not have the suspension to handle the load of a trailer with stuff in the trunk, it just bottomed out and that was that. The 300td has the hydraulic suspension to handle the load, that is why they do not sell the hitch to fit a 300d when it will with no modification.
Good luck
Robert

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84 300SD 84 300CD 85 300SD 85 300CD 98.5 Dodge 2500 Cummins 99 Dodge 2500 Cummins 90 Jeep for the sand Wilmington, NC