Lowering Shackles on a C10 Stepside

[86 Stepside]

I’m DJ and I recently purchased a 86 c10 Stepside. I plan on lowering the rear to level the truck using 2” lowering shackles I bought. I was just under the truck and it appears that the lower shackle bolts will only come out about 1.5 inches and hit the fenders before freeing the spring. My question is do I need to remove or loosen the fender bolts to change those shackles?

Thanks in advance for any suggestions!