If the noise is a serious problem then you'll have to go quite new on your engine options. Multiple injections per power stroke and other electronic wizardry helps the new engines run smoother and quieter than the older diesel engines.
Cummins has a nice little 4 cylinder nearly available for repowers, check it out here
https://cumminsengines.com/repowerThat'd be OK I think for just driving the truck around.
However if you plan to use it like a 2 ton truck then you'll need more power. Cummins will or plans to release a I6 or V8 also specifically for repowers, but after they launch the I4.
For older or used engines your best bet will be the Cummins 6BT. Your choice on how new, if common rail and computers or just a little computers with the 24 valve engine form about 1999, or no computers with 98 and earlier.
Sound deadening products can do a nice job reducing the noise in the cab.
We put a 99 Cummins 24V with a later model Dodge 6 speed in a 2005 F250 and it has been a very nice swap. It is a little louder in the cab but drives so much nicer and pulls a trailer like the 5.4L gas never could. The increased fuel mileage is much appreciated too.
I also have experience with the Detroit Diesel 53 series for repowers/swaps but they're not even close to quiet. They are however remarkable engines, well made and designed, easy to work on, and lots of accessories and parts variations and interchangeability to help them fit in most anything pretty cleanly. I have several friends with them in modern pickups and they are no louder in the cab than our F250 with the Cummins (which has no additional sound deadening with the 5.9 swap).
A V engine will be tight in the old COE unless it is behind the cab but that introduces perhaps as many problems as it solves.
The inline 6 or 4 cylinders will be logical choices. Cummins being the most popular will make for an easier swap than some lesser known and used diesel swap engine, Deutz, Kubota, JD, and any other primarily industrial engine.
Grigg
