^^^this^^^as a general rule the Liberty KK hitch does not fit the Nitro without making some mods, the chassis of the Liberty and Nitro are slightly different, the fact that your hitch as been made to fit both the KA and the KK is where the problem lies,
another forum member "metaldog" i think, bought a secondhand Liberty hitch and came across several issues when installing it,
depends on how much you need to move it back, there looks like there is room to drill 3 new holes on each side, or maybe take it to a welder and ask them to extend it slightly should be fairly easy,
but to be on the safe side i would not move it forward and leave out the 2 rear bolts,
@Nitrogen is correct. I did post a thread on it as I picked up a hitch from a salvage yard off of a Liberty for $25.
It was a close fit, but I ended up with the same issue of the spare not fitting. Ultimately, I scraped the idea and bought the correct hitch and wiring off of Amazon.
After all was said & done I had a perfectly working hitch for around $150.
$25 trailer hitch!