literally any opening in the cab could be a leak (and some that shouldn't be an opening at all). these are the ones I found just on the pass side of the truck I'm fixing up.
I'm fixing the surface rust with a combo of 5way (to chisel up the bulk of the old sealant), wirewheel, grinder, primer, paint and then POR-15. highly recommended that you set up a boxfan to blow a steady breeze through the cab while working (plus mask, googles, etc).