I'm looking for a 16lb VENTED radiator cap. I have a regular 16lb cap, non-vented.... and believe the vented one would be better for my system. I was at the local weekly show last night and noticed a few old mustangs running the vented cap. NOT the cap with the lever on it. It looks just like a normal cap... but it reads VENTED on it. I assume this is to release air build up. Anyhow... I can't friggin find them. Any help would be appreciated. Thanks!!