Transmission suggestions or thoughts

Currently on 3rd g56 in less than 4 months. No crazy stuff, just cruise control at 55 with 40k gross weight and some power. Looking at current reasonable options. The transmissions are ripping the teeth off the countershaft drive gear.

Options on the table:
13spd (preferred, but tons of fab)
6/7/8/9 speed eaton (not preferred unless geared right)
Other pickup transmissions i.e. nv5600?

The truck isn't hot rodded, it is actually babied, the g56 just isn't cable of daily heavy work. It is cooled and doesn't exceed 170f.

Has anybody had experience on any other transmissions being put into these trucks? I have a 13spd in my semi and I've been driving them for over a decade, they shift beautifully and are geared just about perfect, but I'm afraid it won't fit. At the end of the day, it's a work truck and it needs to be able to do just that, so if some metal needs to be moved, that is fine. My concern is starter and exhaust along with driveshafts and transfer case. Not worried about resale as it will get turned into a ranch truck after its career is over.

Who has experience with a better transmission for this pickup?

Tossed around the idea of a MD frame and rear axle with front and cab moved over, but that just seems like just as much fab work.