search around some. There is a whole section of the forum discussing this.
There is also a good post on here about swapping in a VW diesel, but Flash. Comparable power to a 22re I guess. Or you can go with a Factory Toyota diesel. I've heard they are easier to come by in Canada. I'd like one here, but I doubt that'll ever happen. . .
Check out 4x4labs.com
. They are doing Mercedes diesel swaps.
The 5.9 Cummins is a GREAT Motor, but it is WAY to much Weight and size for a Yota!!!
Good Luck and keep us posted as to what you decide. We'd like to see where you go with this!
Also, what kinda diesel does your buddy have?