They sell electronic flashers:https://www.amazon.com/dp/B06XS8VX2W/ref=dp_sp_detail?psc=1
regarding 1157 LEDs, Many will not have enough brightness difference between the low and high 'filaments'.
Many might be bright from directly behind, but nearly invisible at off angles
LEDs get dimmer as they get hotter, so an initial impression of wow that is brighter, could disappear after 30 seconds with ones foot on the brake.
In general LEDS retrofits in housings made for incandescent bulbs is a bad idea. it is likeing someone elses prescription glasses and expecting to see better. Perhaps the prescriptions are close enough that they work, perhaps all is does is make everything blurry and indistinct.
In general older housings with smooth parabolic reflectors and dimples lenses will work OK with many retrofit LEDS, it is the newer vehicles whose reflectors are dimpled, so that each dimple reflects the filament from every possible angle, in which the LEDS will work poorly.
I have some 1157 LEDS in my 89 dodge b250 taillights. They passed my visual tests for brightness differences between low and high settings, and visibility from all angles. I still added a third brake light though.
I cannot find any direct link to the LED bulbs I employed, but they appear very similar to these:https://www.amazon.com/BAY15D-33-SM...038978&sr=1-11&keywords=1157+led
Do not put white LEDS behind red lenses the light will appear purple or pink, put Red Leds behind red lenses.
Also while NO led is actually approved for use in halogen fixtures, Phillips has some LEDs which are approved for use in Some vehicle fixtures. They are pricey, but are well designed and built.https://www.amazon.com/Philips-1157...mp;sr=1-4&keywords=1157+led+phillips
No personal experience with them.
Whatever you choose do make sure it can be seen from all angles and there is adequate brightness difference between low and high settings, and check again after depressing brakes for a minute or two to heat them up.
If you get rear ended and lawyers find out you have retrofit LEDS, it is much mroe likely you will be found at fault or have issues with a claim. Unlikely but possible.
I tried 1157 amber in my fronts but they were obscenely bright, and would not work correctly with my electronic flasher, and I am not adding resistors, so I went back to incandescents up there.