Never thought of the weight issue and wasn't planning on beefing up the front suspension. My build is really close to yours Rusty and what you have relayed to me in the past sounds like it will pull all I need to pull. The 460 was just a left field suggestion and I only had my old man's 76 f-150 2wd to refer to for power. That was also a long time ago so I don't remember.
Like hatemakings/n said it is unique to run a 390 and get loads of power. Even with it all stock it goes good just not what I want and need.
There is less headaches I'm sure to stay 390. After all that is what the '71 was made with!!