I believe any small/short T10 based bulb/LED should work in the HVAC.
I'm using some 7x LED bulbs in mine & they look much better.
The headlight/4x4 switch bulbs are not replaceable, BUT I do an LED conversion that looks MUCH better, brighter & lasts longer than the stock bulbs.
All you need to do is send me your bulb holder (I'm out of extras right now) & I can mod it & send it back to you in a couple days. I have a post here on my LED conversions.
PM me if you're interested.