Off the shelf downpipe?
 

I have a s5 trubo awaiting to go on my '80, is there an off the shelf downpipe that will work well clearing the chassis of the car? Also I have a 13b swapped into the car also.
cxracing.com: Mazda RX7 FA FB 3" V-band Stainless Steel Down Pipe Single Turbo
http://www.ebay.com/itm/Mazda-RX7-FA-FB-3-V-band-Stainless-Steel-Down-Pipe-Single-Turbo-/120997121671?pt=Motors_Car_Truck_Parts_Accessories&hash=item1c2bfd8e87I found these two but they're the exact same thing? Is 3inches too big or should I go with 2.5inches?

i was under the impression that the RB downpipes fit? well they bolt on the turbo and fit the chassis, but you'd need to get it to hook up to the rest of the exhaust

The rest of my exhaust will have to be rebuilt to my muffler due to a rust invasion in the pipes.
I just need a down pipe to start. I can take it to a shop but I just wanted to see what kind of down pipes people are putting on their cars with this kind of setup.

Neither of those will work... they won't bolt to the S5 turbo... and making an adapter to connect to the v-band seems like it would be more effort than it's worth...

I have an Racing Beat 3" DP on my one turbo FB, and the Corksport 2.5" one on my other. Both fit well. Obviously the rest of the system will need to be customized but it's a good start. :)

Racing Beat 2.5in fit perfectly in the FB chassis with a stock manifold and turbo on an S4 block

All I need is a start.
So a fc downpipe fits?
That's really good to hear because I can get a sweet deal on a new HKS downpipe, but I'll go with whatever is my cheapest and best option.

Yeah the FC downpipes fit just fine, at least the ones I've tried.