This may be a bit overdone, but I didn't find an exact answer anywhere. I bought the 2460s, and they came in the other day, but I wasn't expecting them to not be able to bolt up. I'm wondering if it would be more trouble than its worth to get what I need to make it work, since the super comps come with Y-pipe and all. What would make me hand over more money? I'm understanding that the headers can be returned to Summit if need be.
I'm also concerned about this, because I didn't want to do too much mod to the exhaust as I have a 305 and I heard they lose low end with that sort of thing. I'm not sure if having a cat would be enough backpressure to hold it, or what.

 

Repeat over and over until this is thoroughly understood:

"Back pressure is bad."

"Back pressure is bad."

"Back pressure is bad."

Continue if you don't believe it yet.

Flow velocity is what it is all about. Too large or too short of primary tubes is what reduces velocity so that low end power is lost. Neither will be a problem with 2460 Comps or 2055 Super Comps.

Send them back and get the 2055's. The y-pipe is a piece of art. Your cat won't bolt up to it, so get a cat for '86-'90 TPI single-cat application. Your y-pipe won't bolt to this cat, so either modify your current cat-back or get a cat-back for application above.