2006 Sportster XL883C → XL1250C:
Article by Outlaw Mac of the XLFORUM ¹⁾
Click on a pic to enlarge:

Before 2)	After 3)

Most of the tools needed, as well as Teflon pipe thread and 1/2“ washers. 4)

HEAVY DUTY LOW PROFILE CHROME LOWERING AIR SHOCKS Bought off Ebay, Manufacturer Part Number: 116-256 (replaces 54631-02B) 5)

Extra Parts:

$12 air line kit from Advance Auto Parts. 6)	1/8” Tank Valves. 7)

If you want to skip the air lines and just install the Schrader valves;
You can pick them up at the hardware store cheap.

Here's a pic with the part #. 8)

Take off the old shocks and install new the ones, doing one side at a time.

It's recommended to remove the shipping plug AFTER you have the shocks installed. This way you lesson the chance that you may spill some of the oil out if you tip it the wrong way. Then install new 1/8“ fittings onto shocks. Run your air line where you want it and slide on the brass ferrule and cap. 9)

The Teflon tape isn't necessary as in the pic above. That's not what keeps it air tight.
It's the ferrule that keeps it tight.
You just hand tighten the cap, then use a wrench and crank it a 1/2 turn, being careful not to over-tighten.

Make the connections on the other end of the air hose on the 'T' from the kit. Use the little rubber washer like the ferrule on the other end, \ between the cap and the base. 10)

1-1/2” washer were used on the top and 2-1/2“ washers on the bottom to clear the belt guard.
Stock bolt was re-used.
Torqued to 45-50 ft/lbs for both upper and lower bolts.

Eye to eye with stock shocks. 11)	Eye to eye with the air shocks. 12)	Finished. 13)

You can remove the rubber boots and just used 1 O-ring behind the mushroom head of the hose. ¹⁴⁾
No ferrule needed.
A great place to put the air fill, there is a hole in the frame just in front of the battery, around the front corner of the cover.
You can use a stepped drill bit plus 1 size larger.
As for oil, if you ever have to change it, its 10oz.
And for filling with air, you can use a portable air tank.
Fill the tank to the PSI you want and use it to fill the shocks.
Then there's no need to buy a new pump.

See also Road King Shock Oil Replacement in the REF section of the Sportsterpedia.