I was wondering if it would be an issue if i put cats from a vg35 motor on my vq35 motor?

 

Do they bolt up to the exhaust manifolds?

 

.....

 

I don't know the measurements, but they will work... some modifications may be necessary - exhaust extensions if they are too small. Or cutting exhaust pipes if they are too long... modifying exhaust flanges, etc.

Not worth it. Buy some $160 Z1 test pipes or something. If SMOG is an issue, keep your factory cats in the garage for when you need them?