I searched for this information and couldn't find it, so I wanted to post it for others when they do the same search.

The HVAC illumination bulbs in the newer Rangers are 161 type wedge base bulbs. I read several times that the Rangers used 194 type bulbs in the HVAC panel, but the ones in my 2003 are much smaller (no way 194's will fit). Apparently, the older Rangers used the same 194 type bulbs as the speedometer cluster. There are 2 bulbs in the HVAC panel.

You remove the 4 screws holding the HVAC control panel to the dash (after removing the radio/center dash bezel) and access the bulb holders from behind the control panel. No need to unhook anything, it will pull out far enough to allow access to the bulb holders. You simply twist the bulb holders counter-clockwise (clock-wise facing you since they are facing away from you) 1/4 turn to remove them (needle-nose pliers work well....they are small, and it's hard to get your fingers in there), pull the old bulb out, install the new ones, and reinsert the twist-lock bulb holder into the panel. Check function and button it back up.

If you want to use LED's, the 360 degree SMD units from Super Bright LED work extremely well. They are the 74-xHP3 Wedge Base Bulbs:

Super Bright LEDs - Miniature Wedge Base Bulbs

I used "Cool White" in the HVAC panel with excellent results. These bulbs are polar and if they don't work, you simply turn the bulb holder around 180 degrees and reinsert it, or remove the bulb, turn it around 180 degrees, and reinsert it into the bulb holder. 2 bulbs are required for the HVAC panel.

Here's the HVAC panel w/ LED's:






For the speedometer cluster, I used Super Bright LED's WLED-x5 bulbs in "Cool White" (6 total). These are non-polarized, so you can't install them in the bulb holders incorrectly.

Super Bright LEDs - Miniature Wedge Base Bulbs

And they also work very well. They seem dim compared to the above photo, but they are plenty bright, equivalent to the incandescent bulbs. And i'm the type of person that keeps my dash lights up as high as they will go all the time so it would bother me if they were too dim. The SMD's in the HVAC are just extremely bright, maybe too bright. I may switch the speedometer bulbs to SMD's as well, and then dim them all a bit w/ the rheostat. I like how pure white the light is in the odometer and tripmeter instead of the yellow-ish incandescent glow:



I also got Bugmann's LED bulb for the head light switch :





Hopefully that will help somebody when they search for the information about replacing the interior bulbs.