Lowriderghost has the history fairly well documented.  This post is largely an addendum to what he has said and what he has omitted for any reasons of his own.

First, lets talk about some gross history with regard to the frame:

The Lowrider series, comprised of the FXR, FXLR, FXRT, and FXRS models, essentially ceased production approximately in 1993.  I say "approximately" because from 1994 through year 2000 the FXR models continued to appear in dealerships because of the large number of factory parts which required efficient disposal, including the hand-welded FXR frame, last of its kind in the world.  As bikes became popular, it became inefficient for Harley to use the purchased hand-welded FXR frame, and so the Dyna model was born, with its redesigned central backbone and differently angled fork tube stanchion made by computer-guided welding torches.  That is why nothing designed for the Dynas will bolt effectively onto an FXR frame. 

This is important to know if you buy a used FXR, as you had better know welding and sheetmetal work or have a good pipeline to aftermarket suppliers to get parts for this increasingly rare moto.  A replacement fuel tank above the dingy 3.5 real capacity will set you back some 1000Gs from the last remaining custom supplier out there, for example.

THAT said, the FXR frames were indestructible and many will remain long after the cockroaches have taken over from this hapless species.  The central tube is basically an iron I-bar railroad tie going three feet along the centerline, providing amazing rigidity.  In addition, the FXR's generally handled better than almost any other cruiser, including all of the Indians and the Brit bikes.  And with a Stage One upgrade, you essentially had rice-burner performance coupled with good looks.  My '87 bike can actually yank your head back on launch, although MPG aint that great due to gearing.

The FXRT was a chain-drive full-fairing model meant in all seriousness to compete with the Honda Goldwing.  Well, it did have a decent radio and cassette player.

Regarding the EVO engine, you need to know that early models inherited AMF foolishness after the notorious buyback, but each year provided successive improvements right up until 1992.  For example, the primary chaincase oil was free to mix with crankcase oil until Harley realized that this is really a dumb idea; a common fix when the primary cover was off was to plug the hole between the two areas.  The 5th gear doubled as clutch spline and in early models up to 1987, this spline basically had one mickey mouse screw holding the inner clutch hub on to the shaft.  A common failure -- and this failure happened to me -- was that the screw worked loose and the inner clutch hub (forward pulley to you old timers) would hop off and rotate at random on top of the fifth gear shaft.  Made for going uphill real difficult when it happened. And it destroyed the pulley, the shaft, the fifth gear and god knows what else.

Harley eventually figured out it was best to bolt two intimate parts like the forward pulley and the drive shaft together rather than just press-fit them.

Now lets talk about buying aftermarket parts on Ebay.  I have gotten good deals and been ripped off in a major way, and when I have been ripped off its when the seller responded to questions, basically falsifying information.  Caveat Emptor: if the item does not specifically fit your use in the published description, DO NOT TRUST THE SELLER! 

I see "probably came off of an FXR"  and I can tell you "probably" means "STAY AWAY!"

Even for my model year 1987 there were two model designations given, for brakes, for fuel tanks, for a large number of things.  I would recommend buying the parts catalog and using the OEM parts numbers effectively.  There is a reason reputable sellers will include descriptions such as "replaces part 64552-82A".  TRUST THESE GUYS ABOVE ALL OTHERS. 

Now for those odd years 1994-2000 when FXRs appeared to still come out the door.  This is insider info and if captured I must swallow the blue pill before revealing sources. 

Any motorcycle sold as an FXR from 1994 to 2000 was composed of haphazardly "found" parts.  When a manufacturer as large as Harley stops model production significant numbers of assembly parts remain in several warehouses and factories and the value of these parts totals in the millions.  No, a business is not going to simply scrap the material.  Harley assembled any number of FXRs during this period from parts remaining in inventory, plus whatever "makeups" could be found that could be adapted when some parts ran out.  If you have an FXR from 1998, it is quite possible your fuel tank originated as an FLHR tank which had its tang brazed off and replaced with a welded FXR mounting plate.  God knows where the instruments came from and the turn signals.  All FXRs sold between 1994 and 1999 were mongrels.  There is no such thing as a year 2000 FXR.  There never was and never will be.

I have seen parts offered for bid on Ebay which claim "FXR IV model year 2000", which is patently nonsense.  The Dyna had succeeded the FXR by then and no model FXR of that year can be found anywhere. 

As a final note, all FXR models from 1985 to 1993 were given 4.2 gallon fuel tanks and there is no other capacity available, except (incomprehensibly) smaller.  And this claimed 4.2 gallons results in a real 3.5 gallons after the sender unit subtracts volume.  This information was earned painfully and was finally stated emphatically by the local dealership.  "Aint no way you gonna put a five gallon tank on that bike," were their exact words.

And you had better invest in a lot of time and several packages of KREEM  if you buy a used tank on Ebay, for rust does not combust.

See my new posting specifically on buying used tanks.