I'm wondering if there is a way to get a bottom bracket to work without welding. I any idea if I can use a truvativ adapter and an external style bottom bracket.
This is theoretically possible, but not likely with the Truvativ adaptor, which has the threads significantly recessed, so the outboard bearings will likely interfere with installation.
See what i mean?
If you can find the older MRP-brand adaptor, those were completely flush. Barring that, the ones that porkchop sells are almost entirely flush; it'd likely work, but you might have to get obsessive about trimming a few threads off of the adaptor's 3 bolts to prevent interference with the bearings.
http://porkchopbmx.com/Euro-to-American-Bicycle-Bottom-Bracket-Adapter-SILVER-BBIMBA01.htm
Not sure what rear hub you're using, but chainline is a huge consideration; most of the outboard-bearing 2-piece cranks have little or no adjustability in the chainline. Most of the mtb-style outboard cranks will have the chainline too far out for a standard-spaced coaster or bmx hub, but may work OK with a hub spaced at 135mm. Road cranks will have a chainline that will match up with a coaster hub or a bmx hub, but the crankarms won't clear the stays of even a stock Schwinn Deliveri frame. Once you spread the stays to clear that tire, crankarm clearance will be a consideration with almost any crank you run, short of a dedicated fat-bike crankset.
I'm still completely confused as to why so many folks on this build are going thru the expense, hassle, and shot-in-the dark guesswork that goes with the euro and/or square taper conversions, when there are plug'n'play bmx cranks which are designed for use in an American bb shell, with adjustable chainline. Going the BB route tkes out the guessing games, and it makes for a far less kludgy build, and far stronger components.