Get a battery post cleaning brush and use it to clean the sockets really , _really_ shiny clean then smear the inside of the soclet with black moly wheel bearing grease or metallic anti-sieze , this will ensure proper ground of the bulbs , then run a new wire from the mounting stud
of each lamp to the frame , scrape all the rust off where you attach it and use more grease or whatnot (NOT silicone dialectric!) to ensure good grounding .
The twin filament bulbs are P/N 1157 or 1034 , I forget the smaller tag light bulb , we use HD # 631's as they're vibration resistant but only big rigs use them , maybe tractors ? .
A # 532 flasher will speed up the rate of flash a bit .
Good luck !.
