The Huffy number 6H 346743 is the sequence number of that year. They made a lot of them. The numbers on the bottom seem to be the Sears stock number.
"In 1966, Huffman introduced a new long-wheelbase bicycle frame called the
Rail. The new frame was approximately 4" to 5" longer than previous models. The new frame became Huffman's base model until 1968. In 1968, in an effort to market a children's bicycle with an automotive theme, Huffman designers added a car-type steering wheel in place of handlebars to the
Rail frame, which became the
Huffy Wheel. Tall "stick-shift" derailleur gear shift levers mounted on the frame top-tube imitated the gearshift levers of popular muscle cars of the day, while many banana-seat cycles were fitted with tall chromed
sissy bar passenger backrests at the rear of the seat. In mid-1968, Huffman released the
Flaming Stack chain guard, which was designed to look like the distinctive side exhaust pipe covers on the
Corvette sports car. Later that same year, Huffman released a new
Slingshot model with 16" front dragster wheel, and 20" rear. The new 1969 models where the last year for the three-bar Rail frame style."