for us: 3450 lbs car and driver, 512 .indy heads etc:
Removing mechanical fan and going electric, dropped a .02 et
Wilson ported intake , dropped just shy of a tenth.
new converter, cope racing trans- dropped et and improved 60ft.
Dual adjustable front shocks and single adjustable rears - improved 60 ft and et.
Data gathering of afr/vacuum/rpm allowed us to tune and really made us consistent and faster.
Went from 6.72 to a best of 6.38 and car is really consistent in running what Da allows.
( 1/8 mile numbers)

Other than that, just a basic/solid built 511 , low maintenance set up .