I'd like to thank forester2002s and djmark7 for their replies. Since I posted my question I found the bulb issue has inspired threads on every Subaru forum there is. I would like to share what I have found to help anyone who follows this thread, especially since there doesn't seem to be any way to access the old FAQ Sticky Compilation any more. The same steps and parts should work on every Impreza and Forester made from '97 through '01. Replacing the bulbs is not difficult in itself as the bulbs simply snap into sockets inside the heater control. The challenge is reaching them. I found pretty good step-by step instructions by LostInPhilly89 on the Subaru Forester.org forum at https://www.subaruforester.org/vbulletin/f85/1998-forester-bscenter-console-light-replacement-59724/
As for the bulbs themselves, most people have opted to buy standard replacement lamps rather than the OEM Subaru bulbs. Considering someone is selling an OEM bulb kit on Ebay for $26.45, I don't blame them. While the kit includes the bulb for the AC switch as well as the two cluster illumination bulbs, $26.45 is a Lot to pay for three tiny bulbs. Several sizes have been used, including 2721, 2723, BP37, and 74LL as well as the 7219 forester2002s suggests.I compared my car's bulbs with 2723s and the size looks identical. According to my research the 2721 and 2723 bulbs are the same physical size, but the 2721s draw about 1.2 watts while 2723s draw about 2.3 watts. That should make the 2723s brighter but hotter than 2721s The BP 37 and 74LL bulbs are rated at 1.26 and 1.4 watts respectively , are slightly thicker than the 2721 by about .5 mm, and some have complained that they don't always fit. I have no idea how any of these bulbs compare to the wattage rating of Subaru bulbs. Some have experimented with LEDs, but the threads I read said it can be difficult to get good results with them because many of the LEDs out there are poor quality. If anyone wants to try them, any LED designed to replace a 2721 or 2723 bulb should work. One limitation of using standard bulbs is that you won't get the green rubber covers Subaru uses which will change the look of your cluster at night. Out of curiosity I tried to see if I could find them. They are known as light bulb filter caps, or simply light bulb caps, and are available in several sizes and colors from suppliers such as TheToyz.com which sells RC hobby supplies, Speedway Motors.com which sells auto parts, and Jackson Lighting and electrical supply. Most of them are sold in bulk lots of say 10 or more, so buying them for just one car would be rather silly and expensive by the time you pay shipping. If several members got together and bought caps and bulbs in bulk though, making custom light kits would probably be fairly cheap, and you could use other colors such as red, blue, or yellow. I bought genuine Subaru bulbs from Subaru Parts Deal.com. The Subaru part number is 72351FA001 and they cost $4.21 each for a total of $8.42 plus shipping. That's still quite a bit to pay for tiny bulbs, but when you consider that a pair of Sylvania 2723 long life bulbs cost nearly $6.00 at an auto parts store with tax, the difference in cost is rather small. And while I did have to pay extra for shipping the Subaru bulbs, I bought them as part of a large order I would have placed anyway, so the extra cost to ship them was minimal.
Hopefully this clears up most of the issues I and others have had about Subaru heater lights. As far as I know, my information is accurate for all Imprezas and Foresters made from about 1997 through 2001. Outbacks from similar years are different. Perhaps this post could be made a sticky to replace the old one.