Not sure if there were any idler for a flat belt pulley but I do remember my Father had a front hitch bolted to both his 66 and the 77.  This gave an excellent way to back wagons into tight spaces and actually see what you were doing or where you were going without the contortions.  It utilized both holes and was an extremely handy tool.  I don't know if it was available from the dealer/farm supply or whether he made it to suit his needs.