Aftermarket Bmpr Brkt Problems

[71stub]

I bought some aftermarket bumper brackets off ebay for my short fleet and when i put my new bumper up there it sits just about tight against the back of the box just below the taillights and the bumper sits so high i cannot fully lower my tailgate. Has anybody else had this problem? I thought about modifying the brackets but didnt wanna cut a new pair up. How much of a gap should i have between the bedsides and bumper? Is there somebody that makes a good set of reproductions or somebody that has a set of OEM's they would sell me? Thanks for the help in advance!