[BruceLambo]

Hi Tony. Yes the high torque box has the different material for the CnP and a few other small things. But it still has the dreaded undercuts on 5th and the reduced spline sleeve coupler on the input shaft.
My shaft is a lot longer than the wellknown upgrade one as Ive used a chev bellhousing and put my adapter plate between the box and the rear of the bellhousing so the shaft needed to be about 2" more.
I took the original shaft, and a few ideas on paper to a good machining company that deals in shaft and gear design/manufacture. I showed the foreman some photos of a 1-peice shaft, we tossed around a few ideas, done a few measurements and he said "no problem!"
To make the new gears, they simply machined off the gears and shrunk and welded on a new billet, then cut the new gear teeth into the billet and hardened it accordingly. This saved a lot of remanufacturing of the gear. They do this as part of their business and have none ever fail.
The first gear is straight cut because of restrictions in size of the cutting head up to the reverse gear teeth. No biggie.
Ive attached a pikky of my gearbox so far. The diff unit is a 4-spider from a 369 box and the round plate above it is the spacer for it.