For what it's worth, Procyclingstats have Armstrong at 72kg, Ullrich at 73, Savoldelli at 72, Froome at 68, Dumoulin at 69, Basso at 70, Pogacar at 66, Indurain at 79.Even Armstrong (sans clinic) is just too heavy for todays GT. This was only 15 years ago too
Don't know how reliable it is, but it's some ballpark numbers at least. Armstrong had quite a bit of upper body mass, especially in between first retirement and comeback. But if he was active in today's peloton, he'd likely shed a lot of it. Don't think his body type per se was too heavy to make it as a top climber in the modern era.