David Lott at DI as I have a few of his motors in all different power levels. David definitely knows the 7.3. I'll be ordering more builds in the near future, heh, heh.
Brian at BTS does a quality build as well, but I have more experience using his transmissions.
I ultimately decided with going local because both Swamps, NLTD, and David Lott are no where near me and even if they stand behind their product, how in the hell do I get it back to them.....
I didn't know about NLTD, but I could have flipped a coin between both David and Swamp's.
Dave at Swamp's was great to deal with and David Lott was great also. They were both competetive in price, but each did their engine slightly different.
Thuglike (now Jason@NLTD) had a DI engine that kicked some major ass. Docbar seems to be happy as well.
Both great engine builders.
Good luck with your decision. Trust me, it is a tough one to make when going the route you are going. I know....