Recently replaced my burned out speedo bulb on my '01 Chief. Electric speedo, not mechanical.
If it's the same, you should be able to gently pull/pry the speedo out of it's home in the console.
The bulb stats are printed on the base of the bulb. I used a red LED bulb that had the same stats. Popped it all back in, and has been working fine. If you run with a stock replacement, it uses a red sleeve (bulb condom?) to make it shed red light. Mine shredded when removing it.
I don't see any way to shimmy the speedo out. I pulled the 1 bolt in the 'dash' and the trim didn't seem to budge.
Does the entire panel between the split tank need to be removed to get to the back of the speedo?
Not my photo, but here is the Scout 'dash', removing the 1 bolt here didn't seem to do anything. Didn't try to remove the bolt down by the seat.
Got it pulled apart. Had to remove both dash bolts & get it lifted enough to disconnect the speedo cable.
No idea what the replacement bulb is though.
Searching online, a #74 wedge seems close.
It looks like the socket only contacts 1 lead on the bulb.
2001 Scout same no power to the speedo light nor the fender light. Disconnected the speedo cable and the lights came back on. As soon as the drive cable touches the speedo housing lights go out. So far no luck finding the problem.