I really doubt that there is a big difference in the weight of the frames themselves. Maybe a pound or so. I have weighed a few old frames, and the difference between gas pipe and more highly regarded frames is less than what you think. I just weighed a late 70's murray road frame at 6#4oz. A late 80's Schwinn Traveler 4130 weighs in at about 5#. But probably a close to 8# difference in the complete bikes as they came originally equipped. I just turned a 32# Schwinn Sprint to a 25# bike by replacing seat and post, handle bars and stem, and wheelset.