Loving this post, gotten a few more good ideas.

Steering column and box. Manual box is good, but I do prefer power steering as my shoulder is getting bad.
Would there be much difference with an aluminum or race column?

The stock 36 gallon tank needs to go. Thinking instead of a fuel cell, more like a stronger aluminum race one with an internal foam/bladder for safety.

The list is almost endless. Some biggies:
Lithium battery on the framerail under the drivers floor. Save 60# at least of battery and cable compared to lead acid in the trunk.
aluminum calipers, aluminum hats, 50+# compared to stock
Aluminum flywheel and pressure plate 20#+
acid dip bumper brackets 12#

Try the Wallace calculator.

Start with a given horsepower, then plug in weights starting at maybe 4k and work downward to maybe 2500.
You should see a decrease in e.t. reduction as you work away from 4K.

Chrysler used to use a tenth decrease per 100 lbs. removed. But that was typically for most doorslammers back in the day at 3300-3600 lbs.

That was in the heyday of Jr. stock and Super Stock, 1960 to around 1974

My 64 Belvedere just under 3100 w/o driver. The heavy stuff; Mega block, Dana, all steel body stock floor and trunk pans, inner fenders, ect, except hood, std battery, stock steering wheel, steel bumpers. The aluminum parts; seat to floor brackets, brake hubs, calipers, master cylinder, radiator, fuel cell, driveshaft, trans shield, heads, intake, water pump, valve covers, motor plate, shocks, wheels, hood pins, carb air pan, trans drums, front clutch carrier. The missing stuff; heater, wipers, window regulators. The modified stuff; moly tube cage, steering shaft, strut rods, fender braces, center grille support. K frame is cut down, cast zinc cluster is 1/8"aluminum plate. The light stuff; Lexan windows (exc windshield) with nylon straps for functional door windows, vents are Lexan, small alternator. The trick light stuff; magnesium seat frames (seats and brackets together weigh 18lbs each) , carbon fiber bumper brackets (2.5lbs total for all), carbon fiber hood and scoop (17lbs). The extras; plenty of extra cage bars that weren't required for 8.50 cert, fire system, vacuum pump, large radiator, dual fans, 2 carbs, slick tubes. Stuff that I like but is heavy; stock steering wheel and horn ring, cast American 200S wheels, cast valve covers. Except for the safety equipment the exterior and interior appear pretty much stock.
Doug

100# off a car with 100 horsepower makes a much bigger difference than 100# off a car with 1000 horsepower.

No

Look at it as a percentage of weight. 100lbs off of a 7000lb truck is a drop in the ocean compared to 100lbs off of a 2500lb car.

On one of my cars I dropped weight from 3199 to 2987 and picked up 3 tenths and 3mph on the rev limiter through the traps.

I've done nothing but add weight to my chubby 69 Charger with an iron hemi.

At the very least I plan to replace the steel wheels with aluminum look-alikes from Bogart.

I did not do it, but this was done to a road runner I own. There's plenty more, this is just a few areas. The car was raced in this cut up condition for about 30 years. A lot of it could have been hidden, but hey those kick panels and sill plates are heavy don't you know.

Best advice I can tell you is if you are serious about weight, then look everywhere and think in ounces. Gut the platform down to the 'studs' and don't put anything on that you can't live without having.

hows things goin' Itus ?
FMJ still chasing weight ?

I’m gonna pull off that pesky heavy weight fuel tank ...

Nothing. No lightweight. 3760 full race weight,, full cell, both bottles and me in it.. Okay, I do have aluminum Kirkey seats, lightweight racing battery, aluminum wheels, fiberglass hood. All else is all steel, factory windows, full interior, exhaust and street driven.

It's not linear. Lighter the car, the more it matters. HP level also matters some. Depending on the weight & HP, it's close - within a few hun either way. Take it out of a wheel/tire or anything else reciprocating or spinning, it makes a bigger difference.

Where the weight is also matters. Front. rear, and/or how far from C/G in any direction, all make it work differently.