Dash light bulbs

I used cheap Hong Kong ones from ebay in my 65 Dart and they look great. Supposed to last forever, but so where home fluorescent bulbs. Just search for your bulb#. I recently put many LED's in my 80's M-B cars and ran into a few issues. Some (turn signal, running) were too big to fit the car's holes. Some died in 3 sec (looked neat with big heat sinks on body, maybe meant for 6 V?). Some bridged the contacts in the (unique?) M-B dash bulb holders. One started pulsing (could be the brake switch, haven't checked). However, they give much more light. Lighting the dash well is a generic problem with these M-B dashes, but some forward-facing LED's I got worked great to shine light down the "light tunnels" to the dash. Same might work for the plastic light tunnels in the Dart climate buttons (pnuemo-electric switch).