Any body replace front frame rails on a 71-75 A body

Leaving the aprons and core support intact? They will pretty much fall into place. Easier to weld if you drill from the thinner side. Drill through the apron and floor sides to drop the rail out. Use spot drill bits. Take plenty of measurements before, mock-up, measure and weld it in with ER-70s-6 wire. Plenty of guys here to jump in and give advice.