Well,
While I think that the frame would handle the 6V53 with a well designed set of engine mounts, I don't think the 6V53 is a good idea for your truck.
I bought, drove home from CA, worked on, drive around the country, and sold a 61 Ford f350 with a 6V53 and twin turbos. The engine fit nicely in that truck, must have been a lot of work to install, and it was done very well. I felt the front suspension and axle was not strong enough in the ford, the stock brakes were not nearly good enough, and the lack of PS was a serious problem.
There is not room in your COE for a 6V53, it's almost to heavy for the truck, it's just to much engine for your truck.
Stick with the idea of the 4-53 or Cummins 6BT.
