If your springs are re-bushed and re-tempered and back to original you shouldn't have too much problem. If your springs are old and tired like me, you will probably have to at least shorten the rubber bumpers to get a little more travel before you bottom out. I believe you can get a good idea of the new axle travel by measuring the travel available
now and what it
would be by subtracting the thickness of the axle and any bracket material you would need to use. The decision to c-notch would come by comparing the axle travel (and ride) you have now and what you would have after the axle is moved on top of the springs and blending that thought with deciding what kind of roads you plan to travel over.
You would still have to deal with the drag link as mentioned above and if the caster isn't addressed, you will have nitemares with the resulting bump-steer. When lowering a truck in the front, you have to imagine the king pins tilting forward developing negative caster. The stock specs for caster is 0 to +3 degrees. After I put the axle on top of the springs, the king pins were -7 degrees. You wouldn't do what I did, but I rotated the axle back to +8 degrees to run more true at speed.
Charlie Burns Laton, Ca (South of Fresno)

BurnsRacing981@gmail.com