Hemling wrote:
I know that modifications don't legally change any of the vehicle's official ratings or capacities, but what would be the real-world payload difference in switching stock Excursion rear springs with F250 springs? The F250 springs are rated at 3,000 lbs.
Simple answer - check the rear GAWR of the said F250, compare it to your current rear GAWR, and that's your increase in payload.
If you're super worried about the whole legal thing, get your truck re-registered for the front + rear GAWR. Depending on your local law, you may need an upfitter to re-certify a new GAWR, according to the axle's manufacturer's rating (not Ford's).