Isn't a bit premature to consider a major mod like an axle flip? Run it a year and see how it behaves first?
I wouldn't trust any published specifications on something like the axle tube diameter or even which light bulbs are currently installed.
Until you put a micrometer or caliper on the axle and measure it, you've got an x,xxx lbs rated axle that is "most probably" a certain diameter.
The bulbs will be whatever the previous owner left in there. They could be T10, 1156 or LED. If LED, they could be hardwired or use a unique connector.
TT 2015 19RD "TheJayco"
TV 2003 F-350 "Montblanc" - Housebroken chore truck
Sitting in The Cheap Seats.
And proud of it!