I didn't like how sterile looking the light it produced was, and it didn't cast at a distance well.
That's the problem with most (non-household type) LED lamps and fixtures. It has to do with the correlated color temperature (CCT) of the LEDs used.
LEDs around 6000°K seem to be all the rage with manufacturers, yet they have huge spectral discontinuities that our eyes simply don't respond well with (which is why they have that cold sterile color).
I converted the dome lights in my BII to LEDs, except I used 4000°K lighting-class LEDs. These are about the color of a 'cool-white' fluorescent lamp, with less of the cold bluish hue (if I was to do it over again, I'd probably go even a little lower to around 3500°K on the LEDs, still a slight hair whiter than halogen incandescent would be).
If you have the dome with the 2 switched map lights, something from Cree's XP-E or XP-G line of LEDs should work well in it, and shouldn't need any special optics beyond the stock dome light lens to distribute the light well.
Simple resistors are exceptionally inefficient for powering lighting-class LEDs though, you would want a current driver or regulator of some sort to power them effectively. Though I built mine from scratch, there are kits and ready-made drivers you can buy. You just need to match up the driver's specs with the size and quantity of LEDs you plan to use (1A to run a Cree XP-E, for example).
Also be sure the LEDs have adequate heat sinking (I used a piece of 16 ga. copper sheet that fills up the inside of the back of the light housing for mine).
All of that said, if you're not good with circuitry (and hate the cold clammy color of commercial LED offerings), then larger incandescent bulbs are certainly another option.
If you look in the low-voltage landscape lighting section of your local Home Depot or other home center, you'll find a number of wedge-base bulbs that will fit the stock dome fixture. I think I put something like 16-watt ones in my Ranger's dome many years ago and so far I haven't had any issues.
