http://www.oldgravelys.net/pdf/Cart_2_Wheel_Tractor_Op_Manual_0879.pdf
For the tractor in the picture, you would need a roller rest hitch instead of a coupler strut weldment.
http://www.oldgravelys.net/pdf/Roller_Rest_Kit_IPL_19690301.pdf
The very first carts were made of wood, such as the one on page 18 of this document. One Gravely fan still makes the kits to rebuild wooden carts,
http://www.oldgravelys.net/pdf/Power_VS_Drudge_0555.pdf
For the tractor in the picture, you would need a roller rest hitch instead of a coupler strut weldment.
http://www.oldgravelys.net/pdf/Roller_Rest_Kit_IPL_19690301.pdf
The very first carts were made of wood, such as the one on page 18 of this document. One Gravely fan still makes the kits to rebuild wooden carts,
http://www.oldgravelys.net/pdf/Power_VS_Drudge_0555.pdf