Sliding barn door: repair or replace?

Hi, first time posting here. I'm looking for some advice on repairing or replacing the sliding door to my barn, built in 1910. The barn has three stories and sits on a hill: the lower level has stables, the middle level has a sliding door that opens onto the driveway, and the top floor has a hayloft. The sliding door on the middle level has some spots that are rotting away near the ground, and the sliding track is a gigantic pain in the butt, it's rusting and constantly slipping off its rails.



My first priority is to get a replacement that's practical and functional, but I don't want to destroy historical value if I don't have to. The existing wood of the door is 3/4" beaded panel backed by 1" framing, and most of it is in good shape. The inside has a bunch of pencil notes listing amounts of something (hay? grain?) for a series of dates in the 1920s.



National Hardware sells a great set of hardware for building new sliding barn doors: see here. One problem with using it, though, is that it's designed for a 2x4 frame with 5/8" siding on top, giving a total door thickness (including metalwork) of about 2.5 inches. My existing door runs in a slot between the concrete ramp and the floor of the barn that's 2 inches wide, and when it closes the left side slots into a pocket that's also 2 inches wide: see photo below.



Here are the two options I'm considering:

1) Brand new door. Adjust the height so the siding stops above the concrete and only the lower guide rail slides in the bottom slot, and rebuild the barn's trimwork to widen the pocket that the left side of the door slides into. Secondary question: should I cover the new door with T1-11 plywood siding (heavy), ridged metal siding (light, cheap), or SmartSide composite (light, cheap)? None of these is going to match the rest of the barn at all.

2) Repair existing door, replace only the track. This would mean patching several big rot holes in the bottom of the door, one about 6" x 12", several others about 3" x 6", and coming up with a way to keep the door from rotting further. I don't know how to do this sort of patch job so it looks nice.

What do you think?

This could be a great DIY project. The original door was most likely built by the homeowner and it seems to be simple construction and simple materials, yet it has lasted for many years (could even be original).
If the boards are tongue & groove it would be tough to replace just the rotted ones, but if they are simply planks nailed to the backer lumber, you can just replace the whole plank. The tough part will be getting the door down and onto a flat surface where you can work comfortably. Then clean up the hardware (track and rollers) to remove rust, oil it up and stick that sucker back on the barn.

to the site.

Replace. It might save you a few dollars by repairing now, but there will be trouble again soon. Save some work when you can.