A339 and 03902 numbers interchange. countershaft to gearbox belt. I hope photo of mower explains which belt. Probably the easiest way to explain is the belt is by far the longest belt on the mower.
Allen National 68 mower side cutting belts 03931 [ one pair ] made with Kevlar
Allen National 68 mower engine belt 03903 [ Gates 6844 ]
Allen National 68 mower rear cutter belt 03905
Allen National 68 mower engine belt A338 [ older model ]
Allen National 68 mower side cutting belts 03931 [ one pair ]
Allen National 68 mower side cutting belts 03932 [ one pair ] [ older model ] .
![Allen National 68 mower side cutting belts 03931 [ one pair ] made with Kevlar](https://images.buynet.work/thumb.php?i=365892741&s=240)
![Allen National 68 mower engine belt 03903 [ Gates 6844 ]](https://images.buynet.work/thumb.php?i=372704020&s=240)
![Allen National 68 mower engine belt A338 [ older model ]](https://images.buynet.work/thumb.php?i=372704293&s=240)
![Allen National 68 mower side cutting belts 03931 [ one pair ]](https://images.buynet.work/thumb.php?i=372704318&s=240)
![Allen National 68 mower side cutting belts 03932 [ one pair ] [ older model ] .](https://images.buynet.work/thumb.php?i=372704376&s=240)