Where did you get the new U-Bolts? When I replaced my axles, the U-Bolts were supplied by Dexter and fit perfectly. (You should not reuse old U-Bolts anyway.)
One way to reduce the pitch on U-Bolts is to thread a nut onto the end of each leg so you don't bugger up the threads; then clamp the bolt upright across the faces of the nuts in a bench vice, bolt vertical and directly above the vice screw. Tighten the vice to pull the bolt ends toward each other.
You have to overbend it because it will spring back. It is a trial and check process. You may have to use a pipe extender on the vice handle (and you DO need a machine shop size vice).
Be carefull!!! There is a lot of potential energy in that compressed "U".
Others over on the Titanium Forum may have run into this, but I don't remember reading about it.
A