I've never heard of or lifted a stock A body front bench seat that weighed over 100 lbs., I did weigh several different sets of bucket seats and one stock 1971 duster front bench seat when I was putting my old pump gas Duster together, I'm thinking the 1973 Duster bucket seats combine were around 70 lbs. and the bench seat weighed a little more, maybe 8 to 15 lbs.
The 1971 buckets weighed more,10 to 20 lbs. more for the pair than the 1973 buckets did hence me using them
That car had a 400 stroker motor in it and was not built to be real light, it weighed 3450 Lbs. with me in it with extra padding under the carpet and above the head liner, standard steering, heater box and no back seat, five point chrome moly roll bar and a Summit brand 3.0 inch exhaust to the rear bumper.
I move the motor back right at .18 inches and move the rear end forward 1.0 inch, it had 50.6 % weight on the front and the rest (49.4%)n the rear tires with me in it
It would hook up in a mud puddle in a rain storm
Best ever ET was 9.993 at 134,8 MPH using Oregon 91 octane pump swill with the air cleaner and exhaust hooked up and working