Yesterday, during Eric (doghead) and Amy's visit, we drove the 757 around in the same field again. The truck ran beautifully. Not even Amy thought that it was very noisy and Eric noted a turbo boost of 15 psi at one point, no real load, just accelerating in the field. It shifted very smoothly. Going up a small incline, it shifted into 2nd, with a boost of 6 psi and the EGT at 900 degrees.
The axle seal that I got from a spare axle is doing its job, no more gear oil thrown about.
Have not tested the retarder yet, but it does engine brake nicely going down hill by keeping the (auto) transmission in 1-2 gear range.
Amy did get a video of the driving, so we'll wait for their take on the experience...