I have 64K trouble free miles on my '04 Road King. I did a 95" w/cams build at 50K miles. The cam chain tensioner shoes looked like they could go for another 20K miles but I recommend inspecting them at 25 or 30K miles.
When I did the build, I changed the inner cam bearings just because I was in there. I replaced the original cam plate with a new 96" plate and hydraulic cam chain tensioners. I also installed Andrews 26N cams. Andrews makes the "N" cams for this conversion.
If you replace the cam chain tensioner shoes with the original type, the cam chains will be polished and the replacement shoes should last longer than the originals.
I think 2004 is a good year for TwinCam Harleys.

 

The answer to your question, is in the name of the bike... ROAD KING.

 

Brain fart on my part as I was somehow thinking they're like the Heritage Classic bags. My bad.

 

I wouldn’t buy a bike if they don’t know if the tensioners were upgraded. It’s a 12-14 hundred dollar expense if the dealer does a SE Cam Chain Tensioner and Oil Pump upgrade. I had mine done at 30k. It raises the oil psi significantly. Your mechanic should be able to tell just by checking the oil pressure.

If they can’t tell you if it was done I would offer them the price like it wasn’t done.

 

I had an 03 Road King which is virtually the exact same bike. It was a great bike, and I had no real problems at all in about 5 years of ownership. The cam chain tensioner issue is way overblown in my opinion. I have read about them grenading and doing all kinds of damage but I don't think it happened nearly as often as the internet wants us to believe it did. I put over 45,000 mostly trouble free miles on my 03 Road king and when I checked the cam tensioners about 2 months before selling the bike they had just started to show some wear.
If I remember correctly the biggest problem I had with my 03 was the fuel lines inside the gas tank developed a hole and had to be replaced. Otherwise it was minor repairs and maintenance.

 

Riding buddy has an 03 & 04 roadking.
The 03 has over 100,000 & the 04 is around 40,000.
Tensioners on the 03 went at around 80K, the 04 were replaced when he bought it.
The 03 is his around town bike while the 04 is for road trips.
As far as tensioners go wear is not the only enemy, they get brittle.
As far as repair/replacement goes you can spend as little as just over $100 or well over $1500, all depends on what you want.
My old 01 was around $100 my riding buddies 03 went when him & his girl friend were on a trip and it was over $1500.

 

be cautioned about the internal Shifting fork, there is a spot weld holding the input selector shaft to the fork itself that has been known to break and cause you to be stuck in whatever gear it broke in. All aftermarket and current OEM forks have a reinforced weld to correct this problem, service history should tell if it has been replaced yet or not. unfortunately to my knowledge (chime in if you know different!) there is no other tell tail sign to look out for. the part is cheap, like $30, the labor is expensive (about $1200) just a heads up! other then that they are the KINGS for a reason!

 

I had a 2005 R/K custom and I loved it. people under estimate the tw88's I had the 95 kit screaming eagle heads and fueling 574 cam. that bike was a torque monster when I cranked the throttle. I totaled it Last Oct and I sure miss it