Slotting u bolt plate locating holes

Anybody slotted the holes that locates the u-bolt plates (part shock mounts to) to the leafs to move the rear axle back? I had an issue 2 years ago when I installed 3" lowering blocks on my then stock B2200, the drive shaft was just about all the way into the transmission, I have maybe 1/8" before it bottoms out at unloaded ride height with the blocks installed, the blocks are not degree'd. I have replaced my drive shaft u joints due to them being worn out, and after my engine swap, I don't get any noise from the drive shaft like before, but I think the drive shaft should have more travel. I have a 1/4" spacer on the rear transmission mount to lift it up 1/4", without it, it would be worse I bet. I am pretty sure my leafs are not on backwards since it has the mount for the park brake in the correct spot, and I thought maybe the u bolt plate's were reversed, but looking online, they have the same part numbers left and right. Maybe my leaf springs have the locating pin in the wrong spot? I don't think they are original, they have 3 leafs plus the overload leaf. I measured the distance from the front of the rim to the fender, and from the rear of the rim to the fender, and there is about 3/4" less distance to the front fender.

I guess what I am wondering is how much travel should be in the drive shaft where it goes into the transmission? I would guess at least 3/4"?

Not much, the rearend "bolt to the drive shaft" surface goes up and down, the drive shaft goes in and out of the transmission very little, sort of short strokin it. That means the travel in each direction is related indirectly, directly or versa visa.

I added my pinion shims on the top of the blocks, and pulled the axle as far back as I could when tightening the U bolts, and I have about 1/4" play a the transmission, which will do alright for me. The axle twists backwards during acceleration, pulling the drive shaft outwards, but when braking and downshifting it ram it forward, I did a couple aggressive downshifts, enough to chirp the tires, and while holding the shifter, I could not feel any clunk, so I don't think I am bottoming out.

In this instance, not bottoming out is what you hope for, whether a 2200 or any other engine, wave on brave soldier.
If in doubt, it seems the rearend has a locating hole in it for the bolt through the spring, right? You can pull them out, decide how far to the rear you want to move the differential back, center punch and drill the holes undersize, then drill to correct size, reassemble. Does this make sense?