I wonder what the difference is. I would check on parts for the E350 and E450. What year did you get? I heard the change had something to do with a new EPA law but cant be sure.
When I bought mine it was a 2017 and when I did the inspection when it arrived the chassis was a 2016. I called around to 3 ford dealers to confirm the VIN showing it had the 6 speed trans because the early 2016s only had the 5 speed.
My 2011 F250 I was comparing to a F350 and everything is the same with the exception of the springs and I think the sway bar which is why for a bumper tow there is no difference between the 2. Everything else is the same. It wouldn't surprise me if the e350 to e450 was the same deal. Might just need to swap a few parts to make it a 450. The load capacity doesn't matter much. the sway bars everyone upgrades anyway even on the 450. brakes are probably the same, maybe the rear axle is a different gear ratio but that can be changed. Worth looking into and if there is only a few things maybe a few $1,000 you can make it better then the stock 450.
Also with the 8,000lb towing it still only will hold 500lbs of weight on the hitch so you are still limited. I do however tow my 7,000lb boat with absolutely no issues at 70mph.
__________________
|