Positive or Negative Earth?

[KitsonRis]

Total noob question. Hate electrics and electronics.
Currently making a cold air feed light unit, and the side light bulb gets in the way. I have found these bulbs but they are asking for +ve or -ve earth, and either 6V or 12V. As it's from a classic car site I am assuming old cars were different to new ones.
http://www.dynamoregulatorconversions.com/combined-side-and-indicator-bulbs-shop.php

Also what LED flasher unit? Presume a generic one off eBay?
I have the bulb holders saved in my eBay ready, just going to splice them in and modify the light unit to accept them.

 

[Djw John]

Negative earth 12v. Older cars used positive earths.

 

[KitsonRis]

Good job I checked as I was going to gamble a positive earth for some unknown reason haha.

 

[Soot1e]

+ earth went in the early '60's they are all - earth these days.
For LED indicator bulbs any Generic flasher will do but pay attention to the pin layout labelling, there are a few different versions and some can be swapped around by your good self, fiddly but it can be done. You can buy flasher relays that will work LED's only or another version will operate a mix of Led & normal bulbs so both options covered.