Petcock valve for 1980 kz550 ltd

Sorry to ask this, but I don't have my manual with me so I can't reference it. Can anyone help me identify what size the petcock treads are? If not I'll just pull it out and compare it to my friends tap and die set, but this might be easier and cleaner.
Also, I believe I have some crummy replacement petcock on my bike, or I may have a different bikes tank on my frame, because for one the petcock doesn't seem to look like the petcock rebuild kits, and for two, there's no clearance on the gas tank bushings to put a bolt on to secure them in place. (Maybe the tank was meant to do that?) I also don't have a vacuum line on my petcock and I believe I have the line on the carbs, but it's blocked off. Is there any advantage/disadvantage to having a vacuum petcock Vs. not having one?
Thanks in advance!
Matthew

I believe my 550 standard has 2-6mm x 1.0 bolts holding on the petcock.

You can also go to Kawasaki.com and look up parts diagram too.

You can find parts diagrams on kawasaki.com under owner info. Perhaps the thread size is listed there. At the very least you can see what is supposed to be on the bike. A properly working vacuum petcock allows the rider to hop on and off the bike without having to remember to turn the fuel on and off. In other words, the vacuum variety are automatic, while the non-vacuum ones are manually operated.