2003 lance 1171 and 2017 Srw f350 am I asking for trouble?

Dually for that beast. I have a 1055 with a door sticker of 3700. I run down the road at closer to 4500. On an SRW you can do it but not with stock tires and wheels. You will need 19.5 commercial wheels and tires (245/70R19.5 at a minimum) and beefed up suspension component. I ran that way for years. Nowadays I use a dually and it drives oh so much better with that load in the bed than my beefed up F350 SRW ever did