J10 Header Option For 3in Exhaust?

I crashed my hot rod, gremlin x, 550 hp 401. Putting the 401 in my 82 j10.
Gotta have 3in exhaust! My long tube headmans exit so close to frame and Tranny,
I don't think they can fab 3in to attach? Was thinking shorty headers might work?
Anyone got 3in, or even 2.5 in duals from headers?
My current 360 exits through 2in. Dumps in front of rear wheels.
Help?

 

Most headers have 3" collectors and the reduces take them down to 2 1/2. You just need to find some reducers that are 3".

 

My new coated come with 3in! Problem is clearence above crossmember?
May have to go under.

 

Oval pipe?
https://www.racemufflers.com/Oval-Exhaust-Tubing-s/1832.htm

 

That's an most excellent idea(a little pricey though) !
I'm
going to try 2.5 back to mufflers(3in flowmasters), then 3 out the side.
My old system had restrictive (compared to FM), mufflers, and non mandrel bent ells.
This should flow equally well?
Ps-the truck is progressing, have BM shifter in floor and working.
Replaced steering box, and shaft.
Built camo door panels, and headliner.
Repaired tank and fuel gauge now works.
Replaced TC output seals.
Rebushed front sway bar and links(This dang thing corners now like on rails with the
235/70s on!
Still gotta rebuild tilt colum , parts on back order.
Scrapped my winch front bumper, and used my gremlin rear!
Trying to repair all I can before engine comes out