3.5" exhaust

There are size horsepower all over the internet but what I've seen the mufflers and bends are what kill power. The smaller tube you can use increases velocity.
Personally I don't like the look of 3.5 under the car and what I'm planning is 3.5" to the mufflers 3.5" mufflers and 3" over the axle with exits at the rear of the tires.
Exhaust cools and contracts the farther it gets away from the engine so tube diameters can get smaller the farther away you get.
I have a big block in the same power range.