Yes bondo is a major weight adder.
Glenn Gormley's old "war wagon" was an 86 chassis and had been 80lbs over weight for years. He sold it to Austin Newmark our 14 year old racer. Naturaly Austin is a smaller than Glenn so tub weight never seemed an issue. However they started doing body work to repair all the things that caused the car to be called the "war wagon" in the first place. They ran into lots of bondo in places. The one the day the car was some 40lbs under weight.
I think they probabyl pulled 40-50lbs of bondo off that car. Rick your 88 could be the same.