will a 98-02 slp loudmouth cat-back system fit in an 89 with 3" slip fit vin "8"?

Physically fit into the exhaust, probably after you adapt the end at the catalytic converter, and monkey with the hangers. Bolt right up with zero fab? Probably not.

Lol, no cat. resonator.

Using OBX stainless shorty headers w/ y-pipe.

Can deal with the hangers. have a torch and welder. Just not sure about the bends in the pipe to match the tunnel in the floor pan.

The 4th gen exhaust from the middle back, is pretty much identical to thirdgens. The way they route the manifolds, y-pipe, and cat(s) is unique. Should be easy enough to adapt the front to the middle, the back will fit fine.

I've seen a few Third gens around here with the 4th gen Loudmouth and Texas Speed Rumbler. My 3in exhaust system in my bird is actually 4th gen itself.

If you have a welder you can just buy a metal bandsaw or chop saw (if you don't already have one) and make anything work for you. This was made from straight sticks of 2.5" and 3.0" stainless. The amount of money I saved by doing this myself from scratch was enough to pay for 2 bandsaws.

Just found an unused cat-back loudmouth system online for a 98-02. Arrived yesterday. Have other work to do before the car is ready as its been stored for about 8 years but will post some picks later. Thanks for the input.

I have a 4th gen LM2 on my 87 Formy. Unbolt the two rear mounts, swap sides, drill a hole in the rubber on the drivers side, voila!