i am doing a remodel and moved a 2-6 door over a few feet. the original door has a 4x8 header, so I put in the same. My understanding is the header should be affixed by 6 16d nails on each side. because the header was put up against existing framing, I can't shoot through the king stud into the header. Can I toenail three nails per side, shooting through the header, into the king stud?
Yes, toenails will work. In some cases toenails hold better than nails run through the stud into the end grain. The nail head is what does a lot of the work, make sure the heads are set into the surface. It also helps the drywall set better, when you trim the door out you will find what I mean if you don't