[robnolimit]

It's do-able. Oldspowerc10 has done it. Here's a few tips.
1. Trimming the UCA is oK, but you need to put the strength back in it. Forming a length of 3/16" x 1" stock to fit up to the new I.D., and then boxing the arm with 1/8" works great.
2. Move the lower shock mount 'out' on the LCA, to about the inside edge of the bump stop. This will allow a more reasonable spring rate, and reduce the load on the coil over mount bearings.
3. These trucks are heavy, so poly-bushed coil-over mounts are out. Use a bearing mount, a GOOD bearing mount, not the cheapy 1/2 plastic stuff. Also, 5/8" #8 bolts.
4. A 5" travel shock will be close to 14 1/2" at R.H. In a best case scenario, the LCA will be level at R.H. Level from the center of the LCA mount bushing to the center of the ball joint pivit. (not really the arm it self) Get the shocks you are going to use and set the length at 1/2 of the travel, then fab in the mounts.