Replacing Instrument Cluster bulbs with LEDs - Illumination Detail Question - 67 Barracuda

Yup!
There's a lot of talk on the web about needing load resistors on the taillights.
Polarity should not be an issue with Superbrightleds. But, load resistance might be.
There are several past threads, even here on FABO about no real good direct replacements for the taillights and turnsignals.

I am willing to keep the front turn signal incandescent; no problem.
When I piddled around today, I went ahead and disassembled them, cleaning the lens and chrome bezels.
The reflectors are toast! I could not clean them up., being badly oxidized.
So, off again to the store for some chrome spray, before I reassemble them.

I emailed Superbrightleds, and will await their recmmendations on the tail/brake lights.
One of the historic thraeds recommended a Sylvania bulb that would work - but is no longer available.
Exacerbated by the fact you can't even get decent 1157 bulbs anymore.

A possible issue with gauge lights is that some "dimmable" LEDs don't do it well. Some dim a little, then go out. Some dim a little...then flicker like a dollar-store disco ball. While amusing, it would probably get annoying in a hurry.