Header upgrade

Thinking of upgrading my 1 5/8 Hooker Competition headers while my engine is pulled. Curious if there would be a significant power increase by using a larger primary tube setup. This is what I have:
408, around 11.6:1
Ported Performer RPM heads
65cc chambers, 270/232 @.500, 280/240 @.600
Solid cam, 250/254 @.050, 588/600 lift, .010/.012 lash
Rons toilet injection on alcohol
Timing set at 35*
Manual VB 727 with ~4800 stall 8” converter
4.30 gears, 28x10.50 tire
Weighs 3250 with driver

It had a Mopar purple .557, [email protected], .028/.032 lash solid cam that I am replacing with the new one listed above. The old cam was running at 4* retarded. Hopefully the new one works better. Best the car ever ran was 11.01@119 in Seattle. We mainly race at a 1/8 mile track with a 5300’ elevation running 7.20-7.30. Want to run 7.0-7.10.

Like I said it has 1 5/8 hookers into 3” collectors connected to a 3” x-pipe dumping in front of the axle. Was looking at TTI stepped headers, or their 1 7/8. Using a manual steering box, and not using the factory shift linkage. Also looking at ditching the torsion bars for coil overs. Don’t want to cut out the inner fenders.