I'd be willing to bet that Marlin himself doesn't have problems with his 1300:1 gearing so you don't have to worry.
I'm not worried, but I do carry spare driveshafts and u-joints. Driveing style can make all the difference. If you not worried about pushing stuff to the limit, it will break. I've nursed stock birfields in a v8 powered toy for 4-5 years before I broke one.
On the hub gear, just had a friend pop one on 37"s. Chewed up the splines a little on his 30 spliner. In the mail is a new birf and chromo hub gears. I order gears and studs also. Bumping up to 39.5 Iroks started making me think.
