ok one thing i thought about while doing my gsr swap will the gsr cat fit my ls catback or will i need to get a muffler shop to extend my exhaust or can i use a obd1 ls cat in place of the gsr?

 

I did the exact same swap 3 months ago, you're gonna have to put the orignal ls headers in place of the gsr headers. The ls headers are longer towards the cat and the o2 sensor is right on tact, whereas gsr o2 sensor is a little up forward. The gsr headers are shorter than ls, you can go gsr headers and have muffler shop extend it, but with that money, i'd save it for some headers.

 

so just use my ls headers with my extra obd1 ls cat? the gsr is obd1 also

 

your entire exhaust will work just fine