On my 1969 cutlass when i turn on head lights the high beem indecator and right blinker indecators come on dim after i drive for a while they will disappear and also the gas gauge when you turn head lights on will drop about a 1/4 tank turn lights off goes back up lol anyone had this issue

 

Clean and check the front turn signal bulb and socket. Sounds like the socket is crusty and you have current from the taillight circuit back feeding into the turn signal circuit. Make sure the cmsocket is well grounded.

As for the high been indicator, check the condition of both headlight sockets and terminals, and the grounds on both sides. Once again, sounds like stray low beam voltage is finding it’s way into the high beam circuit.

As for the fuel gauge, make sure the body ground from the negative battery terminal to the body is in good condition. There is also suppose to be a ground from the rear of the engine to the body. There is also a jumper wire ground from the fuel gauge housing to the speedometer housing, it’s easy to miss, but difficult to get to.

Be very careful if you remove the connector from the fuel gauge. The pins on the circuit board are very fragile, it’s easy to pull the pins from the board.