bought the shocks off of another HD forum for $90 shipped, they are the 12" street glide shocks.. but they turn up on eBay all the time pretty cheap, you also want the later model shocks as they are designed to hold more air than early on, i believe 2006 was the change over year..
here is a list that someone compiled of part #s and sizes, makes it easier to shop the sites and eBay
54565-09 FLH FLHT FLHR FLHTI 13" (G5E3-00)
54565-97 (A) FLH 13"
54565-97 (B) 13"
54565-97 (C) 13"
54631-02B Road king FLHRS or FLHX or FLTRX 12" shock pair "low profile"
54632-98 bagger 12" or 12.5
54661-02A Road King FLHR Street Glide 12" single shock "lowered"
54662-09 street glide 11.5"
there are many different ways to change the oil listed on various sites online but for me the easiest was to pull the fittings and hang them upside down on a slight angle, got 11oz out of one shock and 10.4oz out of the other.. the box they came in had oil residue in it so i assume that's where the other.6oz went. refilled each with 11oz of 10wt bel ray shock oil and as i said the ride has been amazing to say the least..
since my bags are removable instead of air lines i went with 2 separate schrader valves because i didn't want to see the lines with the bags off the bike, i picked them up at ace hardware for $2.99 each and they work great..
only other thing i can add is if you go the air shock route make sure you buy a shock pump that does 1lb increments so you can dial them in, a lot of the pumps listed on eBay
only do 2lb increments..
this is the one i bought nearly 2 years ago and it still works great