Help with Stock 57 Chevy Truck Blinker/Brake Wiring

[69MyWay]

I am working on a 57 4100 series truck for my neighbors landscaper. He actually uses this truck daily in his business. It is about as stock as you would imagine for a vehicle that has been in continous service for 49 years.

Anyway, the brake/blinker on this truck is not a combo unit. In other words, the brake light switch goes straight to a dedicated pair of brake lights, and the blinker goes to a park/blinker pair of lights. There are FOUR lights on the back of the truck.

The blinker switch is a THREE wire unit not designed to run the brake signal.

Here is my question.

Can I put a diode in each brake light wire just before the lamp so all four lamps have brake lights and blinkers? That would prevent the power from backing into the other lamp when the blinker is on.