Re pinion angle, what should i be aiming for?

Good idea about the b350 leafs. Or do i put the axle back and remove a leaf.....would gain clearence between frame and axle.

Same angle as trans output, but different plane.

Natural has a 6" "C" notch in the frame and had the floor pan raised in the center of it. My diff still hit the floor pan on hard bumps. The shock mounts at this point are too far forward and only provided lateral dampening, none for vertical. Pinion angle IS a very important item to look at. Otherwise everything in the van will vibrate apart, or lose endurance to vibration, etc. I know...
Natural currently sits with the axle flip, but also flipped shackles to raise her back up a bit for a smoother ride. If you can afford air and can have proper welding done into your notches, you may be able to do it. Depends on your intentions with the van, and your resources...

Could you elaborate on the flipped shackles?

I have the gas tank filler hose that runs between leaf/shackle and body, did you have to contend with that?

My c notch would only cut into the frame rail, not the floor, not enough??

Your last photo, ride height looks higher than first?

My shackles are stock units flipped down (disconnected to get around filler neck, then re-attached downward). So, yes, the last photo has a taller ride height than the first by a few inches. A 3" C notch would keep you out of the floor pan, but may not be enough to keep the diff from hitting on hard bumps if that is your ride height during cruising. If you bag it and drop the floor onto the diff during parking, but raise it for driving time, that would be different. I also would worry about floor strength if you only have a 1" frame rail for that small section, it still takes a lot of movement and abuse during acceleration torque. I would advise notching through the floor and raising your floor pan up to the top of the notch rails, instead of the bottom. I wish I would have. That would allow me to relocate my shock mounts and keep the lower ride height without bottoming the diff on the floor. I hope that I can help you in this rather than raise more confusion. Just worrying about strength to keep the van and not fold it, or twist it..

Going to try and get the shackle done this week. I concede with a 3" notch its prob not enough travel.

So have been looking at air bags.

FIRESTONE kit mounts between the rail and bolted to axle inside of the leaf spring. I prob dont have enough clearence at this location to squeeze a bag in and have reasonable inflation to stiffen ride up, ie prevent bootoming out.

AIRLIFT kit mounts outside of rail and bolts to leaf/perch. With the axle flip may need a custom mount to axle. Notsl sure if top kount would foul the c notch.

What about mounting bags behind the axle, not over. Or even inside the frame between the pumpkin on each side. I would gain space for the bag and declutter the cnotch axle area.

So I bought a 2 inch block kit from autozone today. I was planning on flipping the axle on my 91b350 I'm not welding anything or spending a ton of money on my van because its a rot box. Would it still be drivable?

What I'm asking is should I opt for the "lowering shackle" kit from AZ, or a block and flip kit? I'm looking for just an off the shelf deal for cheap..

bit of an update...

I notched the frame, used 8" pipe cut it in half as the notch. used a plasma cutter and cut out the frame rail, centered on bump stop. welded the half pipe into place....worked perfectly (so far)....with the axle flip I have enough travel.

If I knew now what I know then or whatever, I think the way to go is to remove a leaf, the axle flip is too low by 1.5-2"...leaning to adding airbags to lift it a bit....

Fronts....big pain in the ass. but finally got a spring out. cut off 3/4 of a coil and shoved it back in. I dont think it did much. I know it has to settle and the van aint driveable so I cant really seat it to see how low it should settle at....think the springs were tired to begin with and the first coil was already resting on the second so I may have just cut off a dead coil.

Should I give it some days to sit and see if it does settle down lower?

was able to speak to a tech at RideTech. wanted to install an air bag over the leaf pack to raise the rear 1-2" inches, it sits too low after the axle flip.

in a nutshell, said it wouldnt work. Not intended to raise the ride height above the leaf springs factory hieght, only support in overload situ....makes sense i guess. weight must be burdened by the spring first, then bags.

So, must tackle rear again. Shackle flip as suggested or remove and/or de-arch a leaf...

That shackle flip, I am up against the blasted fuel filler neck and the peculiar b2500 rear shackles....very wierd design. Might see if I can swap the shackles out for more standard fare...