I was at 80 psi, my normal with the 395's. Taken it down to 65 psi before and the sidewalls flex very well at that pressure, just was being lazy. The rest of that trip was basically 1000rpm low range 1st/2nd/3rd just crawling right along.
Mine has the same low/high shift stubbornness. I would split shift the m35a2 every time but this one is stubborn so usually I stay in high for on road and low for offroad. Eventually will swap the trans but that's a few years away. Would like to go with the CAT 7155. With power upgrades the truck will get a holset ht3b turbo and after that a dual fuel line mod. Hopefully next year for that and jakes. Will admit though for everything I've read on here about the wreckers being super slow, this ones not. When Valence and I were convoying out for the offroad trip he said that up through 3rd gear his m35a2 was faster, but above that my m816 was walking away from him. Ain't a speed demon but it handles itself well.
The locker is a Detroit so it's mechanical. Going to place it in the middle axle when the weather cooperates. Looking forward to the extra traction, cause it sucks when a wrecker gets stuck.
With the rivets holding the brake backing plates on the rear axles, they suck ass. Ran out of gas for my torch so was having to use a cutoff wheel for the rivets it can reach, which is only 4 per wheel end. The other 6 per end will have to be cut off some other way. Thankfully for the trade he only needs 4, so I pulled the backing plates off the m51a2 front axle to provide 4, and pulled the components (shoes, wheel cylinders...) off the rear axles of the 816 since I know they work fine. Going to take the torch to the rear backing plates and remove them in pieces since they are now destined for the scrap pile.