Anyone that has the old style cam chain tensioner/oil pump setup(pre '07 I think) should read this. It will save you time, maybe some money, and headache. I have seen many threads and posts on this subject, but none that are complete. So this is my attempt at that. A 20 minute call to Fuel Moto cleared it all up.
My bike has almost 50k miles. 2001 FXST.
I am about to replace my stock setup with the SE hydraulic cam chain tensioner /oil pump upgrade kit part# 25284-11. While I'm in there, I am installing Andrews 21N conversion cams. First things first...
I found the kit at Newcastlehd.com for $423, compared to the normal MSRP $499.

On the HD website, it says the SE hydro/ oil pump kit requires seperate purchase of 3 kits to install:
SE install kit part# 17045-99D $110
Spacer kit part# 25285-08 $20
Drive gear retention kit part# 25533-99A $7

The install kit(#17045-99D) is essentially the exact same kit as their cam install kit. In fact, if you google the part#, it is listed as a cam install kit on some sites. It contains what you need, but also many unnecessary parts which are not model specific. Also, This kit contains parts that would only be used if you are replacing your cams from the top end(removing the gas tank, rocker boxes, etc). Which would not require purchase of adjustable pushrods(you would reuse your stock ones). So, many gaskets and seals are not used- if you are going the adjustable pushrod route. Fuel Moto sells a model specific cam install kit for about $50. It also contains parts that would only be used if you were going in through the top, but it's half the price. NOTE: the FM kit also comes with the Torrington B-148 bearings, not the INA bearings you will get with the SE kit.
The spacer kit(#25285-08) is needed. It comes with different spacers, only 1 of which you will use, but you will not know which spacer to use until you get in the cam chest.
The Drive gear retention kit(#25533-99A) is literally 1 bolt. For $7. The OEM rear cam bolt can be re-used(assuming it is in good shape), make sure to loctite it in.
You will have some O-rings that are left over, as the SE Oil pump upgrade kit will come with many of the ones supplied in the cam install kit.

So if you are only doing the SE hydro kit, or doing both that and a cam swap, you only need one install kit. Whichever kit you buy is up to you. I personally like saving money.

In addition, The SE hydro kit recommends the re-use of the stock "silent" chain(inner/secondary cam chain). Only the primary/outer cam chain is upgraded to the new roller chain style. It has been said that the old style silent chain will cause premature wear on your new hydraulic inner tensioner. I for one, do not want to risk that if I'm going through all this trouble. So, you can purchase a roller style chain for the rear/inner from HD(part# 25683-06) to fix that.

Hopefully this clears that up for some people. It was all confusing to me.

And before anyone says anything, no, I am not associated with Fuel Moto in any way lol. Just definitely a returning customer now, they have great service.