Stan, it doesn't look like we've established whether you're working with a 6 or 12 volt system. From what I can make out on the SAMS radio specs you posted, it appears to be rated at 6 volts.
If that's the case, then 1157 isn't the bulb you want for rear stop/tail lamps because that's a 12 volt bulb. I just replaced the after-market tail light assemblies on my GMC with 6 volt originals that take two separate bulbs for stop and tail. I can probably dig up one of the old 6 volt dual filament bulbs and give you the number off of it. I also have aftermarket turn signals up front, and those are single filament bulb #1129 which is probably what you need for yours, unless they are double duty parking/signal lamps, in which case they'd be the same as the dual filament ones I removed.
Let me know what type you need and I'll get back to you with numbers. I basically have bulbs for all possibilities here, be it dual filament front & rear or single filament.
If that's the case, then 1157 isn't the bulb you want for rear stop/tail lamps because that's a 12 volt bulb. I just replaced the after-market tail light assemblies on my GMC with 6 volt originals that take two separate bulbs for stop and tail. I can probably dig up one of the old 6 volt dual filament bulbs and give you the number off of it. I also have aftermarket turn signals up front, and those are single filament bulb #1129 which is probably what you need for yours, unless they are double duty parking/signal lamps, in which case they'd be the same as the dual filament ones I removed.
Let me know what type you need and I'll get back to you with numbers. I basically have bulbs for all possibilities here, be it dual filament front & rear or single filament.