You can probably make sure the brightness is turned up, and try 168 bulbs to replace 194 if necessary. That's what I would do. Also clean up the ground connection for the instrument cluster, and clean up the printed circuit where the bulb holder contacts the circuit and where the plug fits in the circuit. I used Brasso to get the metal nice and shiny.
Edit -- Adding hardly see the speedometer numbers is sometimes caused by aftermarket lenses that are printed incorrectly. There is a thread here on the forum where it was discussed the lenses being done wrong. So if you have a new lens that could be the problem.
https://www.67-72chevytrucks.com/vbo...d.php?t=813854