Maxitorque 6 speed twin stick to maxitorque t310es

[Eriksf250]

Good evening everyone, I have an 84 R model at work with a 237(originally a 300 truck), maxitorque 6 speed twin stick. It has 11r22.5 tires, 38k rears, and I believe a 5.something gears( does about 68 at 2300 rpms. It's finally getting some much needed work (turbo, exhaust manifold, intercooler, air compressor, gasket revealing, valve adjustment, torque arms, air dryer, radiator, and pulling the transmission because some of the bolts for the transmission to flywheel housing were either loose or missing. I'm trying to talk my mechanic and boss into switching out the transmission for something with more gears and an overdrive to keep the rpms down on the highway a little. We've had some granites with the maxitorque t310ES 10 speed transmission and I really like how it's setup and shifts. It will retain the multispeed reverse like the 6 speed, has low low gearing for heavy loads like the 6 speed, has better gear spacing for that 237, and has a .73 overdrive. My question is, will that bolt in directly in place of the 6 speed without modifying driveshaft length and be able to use the existing flywheel housing? I know air will have to be plumbed and probably a new hole in the floor for the shifter. Will the mechanical speedometer work with it? I was also thinking of the maxitorque T2090 as well since that's an overdrive as well. 

Another quick question too as far as the engine. This truck was a 300 and now has a 237.are the turbos different between the two? Would there be any benefit in power? Just curious lol. It's the truck on my profile hooked to the 55ton lowboy with a 330 cat excavator on it

Edited 20 hours ago by Eriksf250