Looking for correct bulbs for 1965 Plymouth Valiant 200 for Instrument Cluster

158 is the old short-life version of 194.

158: 3.4w, 2 candlepower, 500 hours
194: 3.8w, 2 candlepower, 2500 hours

The '65 I owned, and I'm pretty sure all the '65s I took apart over the years, used the metal bayonet-base bulbs (53, 53x, 57, 1891, 1893, 1895…) in the dashboard. '66s definitely used the all-glass wedge-base bulbs (158, then in later years 194).

There's a ton of junk on the market in LED bulbs. For reliability and safety (including fire-prevention safety) you're best off sticking to legitimate bulb makers, rather than the gumball-machine trinkets with no engineering behind them from StupidBiteLEDs and other such vendors. Good ones to fit the bayonet-type sockets in earlier-model cars are practically unavailable. The workaround, if you've got the bayonet sockets, is to buy the wedge-base sockets. That's these (sold individually, one "each" at the listed price, even tho the pic shows two—hence why two buyers left upset reviews, thinking one money got them two sockets) and install the good bulbs. That's this yellow-amber one, top pick for general dashboard illumination, much brighter light without glare that you'd get with the white bulbs. The yellow-amber bulbs work well behind green lenses in turn signal pilot lights, too. Red (high beam, oil pressure) is this one. Cold white is this one, and warm white is this .

The only "gotchya" points are minor: LED means Light Emitting Diode. A diode passes current in only one direction, not both like a filament. So if your car has a single green pilot light that flashes no matter whether you're signalling for a right or left turn, don't put an LED in it; it'll only work when you're signalling one direction, not the other.

And for the rest of the dash lights, it matters which way round the bulb is installed in the socket (or the socket in the circuit board). If the LED is installed backwards, it won't light when it should. If there are other LEDs in the system (as there are in the dashboard) then just one backwards LED can create weird new paths for electric current that shouldn't be there, causing a no-light or no-light-when-supposed-to or light-when-not-supposed-to situation.

So, fashion a jumper to ground the cluster properly (when installed in the dashboard it grounds via dashboard metal). Install one LED bulb/socket assembly. Try it out to see if it works correctly. If it doesn't, remove it, turn the bulb or the socket (not both!) 180°, and reinstall it so it works. Then move on to the next one: install one more LED bulb/socket assembly and try it out. Proceed this way until all the bulbs are installed and working.