Couldn't tell you where else to get them, I don't know, sorry.
bbtank, all the diesels have the 4,000lb axle and the gassers had the 3300lb, so when we need parts, we have to say 4,000, even though they will tell you a 250 will have the 3300lb.
If your truck is 2wd, it is a D350, like mine, not a W350. The D series trucks are 2wd, and the W series trucks are 4wd. Also, we don't have a front "axle", the 4wd trucks have a Dana 60, we don't, unless someone converted it.
I love my DennyT cone, and it made a very noticable difference in my auto, so it shoud be a real bid difference in a 5spd. I would have no problem spending the $105 again, (it was actually $100 shipped when I got mine though...) and it is easy to install.
You can get it on
Denny T Performance | First Gen Dodges and I beleive that site has instructions.
A great mod for these trucks is the 366 spring, which replaces the stock governor spring. The 366 spring allows the truck to FUEL to 3200 RPM, where the stock spring limited fueling to around 2400 RPM. Very helpful with the 2-3 shift.
Before any fueling mods, especially in a Non I/C truck with the big injectors and small turbo, I would suggest gauges. Al least pyro and fuel pressure, and I would also suggest a boost gauge.
If you need links on how to install the 366 spring, or DennyT cone let me know, I'll post them up. Or if you need more information on how to make her run a little better, I'll answer any other questions I can.