I really like the way they look. I was thinking the same thing with my 90 after I installed the flatbed. I don't want the stacks hitting trees off road.
Dunno about how loud they would be, the little experiance I've had with my brothers stacks, resonance can be changed with differnt mounts, and different heights. His stacks were real tall turned out 45*and quiet in the cab, then he cut them down(they are bull haulers) so they were slightly taller then the cab. Then the truck got real loud in the cab, and it was resonance. He made a little better mounts, and turned the stacks straight back, then they didn't make your eardrums bleed. I think the pipe you use before the stacks, and how its routed will effect the noise in the cab. I know a ve pumped first gen sounds differnt the a p-pumped or 24 valve truck, so I think the sound will be differnt with what you hear in the cab.
Let us know what happens, cause mine will be that way. I need them short to keep away from trees, but can't be under the truck so water and mud doesn't get in. Plus people on the trail won't like smoke in the crowd, so it needs to go up in the trees.
Michael