Yes you can get it to fit, in the vehicle. But the buckles are not the same size. the female from a XJ will not click together on the male end of the wrangler belt.
I just installed a wrangler seat belt in mt xj with very little problem, it was nearly bolt on. and my wife have the exact same seat belt in her yj.
1989 XJ, 5spd, np231 with bjconversion SYE , re3.5, 33x12.5r15 BFgoodrich ATS, D30 F, Dana 44 from 87 with 4.56s, Custom front bumper.
94 yj: stock everything and 4 angry squarrels under the hood.