Will "shorty" style headers bolt up to the stock cats (race pipes in my case) and longtubes replace the header and cat?

Also, have people had fitment issues running brands such as megan v. stillen? I would like to run a stillen header since i already have their race pipes and y-pipe, but if i can spend $200 bucks on a megan and get the same gains, I will. Anyone have positive or negative experiences on any brands? I think i would prefer the shorties, since I already spent the money on race pipes, just to keep the system modular.

Thanks.

 

bump for a good question

 

I read about a few people having fitment issues with the long tube headers from megan. One issue is you have to dent one of the pipe for clearance purposes. If you have the extra cash I'd go with stillen or maybe DC?