‘03 Add a Leaf / Leaf Bushings - Question

‘03 PreRunner DBL Cab/3.4l, Auto
A couple of weeks ago I changed out the front suspension to the OME 880 coils with Bilstein 5100s (set at 0). Love it!
The rear now seems to sit a little lower which I sorta expected. Rear has the stock springs with Bilstein 5125s.
So, I ordered from Low Range the Add a Leaf springs and the OME U Bolts (little longer).
I did spray liberal amounts of PB Blaster on the leaf spring mounts the night before starting this.
While waiting on parts to arrive, I removed the passenger side leaf spring yesterday to replace the original bushings with the Energy Suspension poly bushings.
I don’t live in the rust belt so wasn’t expecting to much of a difficult time......MISTAKE! Sonavu! Now I understand why people just cut off the shackle bolts. I basically bent mine and the rubber was welded to the bolt. Went ahead and ordered two shackle replacements this morning in case the drivers side is bad.
Took me about two hours to get the metal sleeve out once the rubber bushing was removed.
Achieved by heat, a hacksaw, and a chisel.
I’ll post some pics when the Add a Leaf springs are installed.

https://www.lowrangeoffroad.com/toy...ux-rear-add-a-leaf-1-5-2-lift-pair-13120.html

 

that's why I'm glad when I researched I ordered the full kit with greasable shackle bushings and new shackles, didn't have to deal with that. that being said for some good reason (sprayed underside of truck frame/body every year) I did not have any real issues save for the U-bolts needed to have some heat persuasion (yay for a mechanic in the family)

 

Got a question for you guys. What can you do to prevent the rust from coming back inside leaf spring bushing mounts (pics below)? The front of the spring (facing towards engine) wasn't nearly as bad as the shackle mounts. I've read where you are only supposed to put grease, etc., inside the bushing itself, not outside the bushing.
The pic below is the shackle mount after using a wire brush and dremel.

 

Got the hangar bracket stripped and ready for POR-15.
Anyone know what the “1” stamped on the bracket means?? Pic below