I have a 1972 iwth a similar problem and the two different lenght ears. If you had to summarise the approach - and i wanted to just buy a threaded piece to use - what do i do/
Do i put a brass screw 4g weight (of whatever dimensions roughly you have there) into both floats?
How much do i sand off and is it at the bottom or top or sides?
And finally - have you put these in your car and has it solved the issue?