If you want a "built" Cummins then contact your engine builder of choice
Ray-Mac (High End Racing Motors-Diesel, Gas, Alcohol, Nitro, etc... )
Fletcher (Diesel Specific)
Haisley (Diesel Specific)
Sheids (Diesel Specific)
Piers (Diesel Specific)
Mitchell (Diesel Specific)
Etc. .
Everybody has their own preference. This is just a short list of some of your options.
Check out my sig for more info on my choices.
I use Ray-Mac for a few reasons
1. Ray Little has an excellent background in racing motors and I wanted to see what he could do with a diesel.
2. Location Ray-Mac is located about two hours from me.
3. Compatibility Ray has been extremely easy to work with. I can always get in touch with him. As well as he is willing to try new things upon request, and willing to share some of the so called "secrets". Also when you get a motor from him, you also receive a build book with every spec from the motor-clearances(bearings, ring gap, crankshaft endplay, etc... ), weights(pistons, rods, wrist pins, etc... ) and so on.
If I had not found Ray-Mac then I would be using Haisley Machine.
They provide many of my hard parts, and have always been good to work with. Their location just makes it a bit hard for me to use them on a regular basis. But, they have provided me some great parts and trick pieces.
Hopefully this doesn't start a war, I don't intend to. Thesse are just some of my preferences.
~Wes~