37 Imperial roof question

Couple years back a buddy picked up a 38 Plymouth truck that had similar damage... Trying to help I found him a dodge cab, but instead he found an old bodyman that fixed it for him... More than 90% of the damage was fixed the first day.... That last 7-9% took the reast of the week.... No plastic filler, perfect gaps.. He insisted that old thick steel is easier to work than the stuff used these days...