I'm swapping a rear end from a 97 m edition into my 91, I heard there might be issues with the brake hardlines since the 97 had abs. Am I going to need to change the hardlines or should it work fine?
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Rear subframe? Isn't miata ABS 3-channel so brake hardline shouldn't matter on the rear end. Or are you talking about the hardline that bridges right and left from the distribution block. That should be the same too.

 

Thanks that's what I was thinking but my friend who is helping me with he swap was thinking otherwise and we don't have my subframe out to compare.

 

If it means anything, I swapped an NB rear subframe into an NA6. Everything bolts on the same. I upgraded to 1.8 calipers since my 1.6 ones were seized,all on mtuned brackets and sports rotors. All other parts bolt on as usual. I even bought a brand new crossover hardline and clips, just swapped right in.

Post pics of your conversion

 

The exhaust hanger on the subframe is a little off if OP is trying to reuse an exhaust. Nothing that can't be worked around with some clamps and some ingenuity

 

Oh, I guess that is a thing. I have an aftermarket exhaust so I never really encountered troubles with less than $60 of modifications