i don't know what material the shackle bushings are made out of. but who ever you buy it from should, so i would call and ask them. on the front bumpstops, they will be completeley bottumed out once you drop it. they will sit on the upper spring pockets. i just cut about 3/4 inch of mine to allow for some travel because i'm not aware of anyone who makes shorter ones, but there couls be somone out there. i wouldn't cut too much off of them because it will halep you keep from bottuming out, i wish i would have only cut them like 1/2 inch. i would just cut them a little at a time till its right 
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'51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works
'05 1500 Crew Cab
RIP
'84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker
'80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's
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