Just wondering how much modification id have to do to fit a “BOR-17202” header onto my 91 h.o. into my 89 xj. If any. This thing is getting torn apart anyways so im up for almost anything.(edit:the header is meant to fit a 00-06 wrangler)

 

1999 4.0 head has smaller exhaust ports, can't confirm but I've read that late model manifolds will not cover the larger exhaust ports of the earlier heads.
Welcome to the forum, there is a thread for exhaust questions or you can post in the modified xj tech section.

 

this answers the question.
i’ll look into this more in exhaust questions tomorrow as i am about to go to bed. Thanks a bunch!(been lurking the forums for a long time finally made an account this place has been pretty helpful)

 

If the head that those headers were made to fit is a 0331, you might have issues...is the header a 2 piece with 4 O2 sensors