Weight reduction is one the most important factors, along with balancing... side-to-side (l-r) for each half (f/r).... with the driver and as you plan to drive/race it the majority of time.

Front seats can drop weight 20-30-40 pounds.

Master brake cylinder.. go with aluminum. and consider keeping or removing the power booster.

Radio stereo? eliminating all can reduce about 20-30-40-50 punds, pending what you have.

Do you need the passenger door mirror?
Do you need a front and/or rear spoiler?
Carpeting and insulation?

The list from everyone can be further expanded.

But, are you considering running in any sanctioned organized club events that have RULES/restrictions per your chosen class? consider your choices. IF you're an outlaw... running without RULES for mods of your car, then there's no limits, but, if you choose to run competitively in a sanctioned club event with RULES/restrictions, then decide ahead and make your mods very selectively. In other words, you don't want to over-or-under-mod your car then find yourself not competitive... and not happy having the fun you're hoping for.

With my own Challenger T/A (cloned long time ago, back in the 70's.. 80's), I followed the SCCA E/Street Prepared Solo II class rules for any mods done to the car... was ultimately able to get the weight of the car down, legally, to ~3150 (1/8-1/4 tank gas) w/o driver, with ~52f/48r% balance, and also had the side-to-sides equaled nearly same to each other... with driver as raced. Its also street/hwy driven.. raced seriously and highly competitively at AX/HSAX/HPDE events.

My battery (lt-wt Optima) is located far r/r of the trunk...as that's where the scales showed it to be best located. I tried it centered above the differential... scales showed it better far r/r. Overall, car handles great!