I am missing one headlight bucket for a 70 chevelle,and dont know which one I need.Currently I have 2 buckets with a square hole in the back and 1 bucket with a round hole in the back. Is this the difference between high and low beams? I dont know where to look to find the letters "A","B",etc...Any help is greatly appreciated.... Joe

Can anyone help me with this??

Joe, all four buckets should have the same shape hole in the back. The shape is basically a square with the corners cut off. The letter A,B,C, or D is stamped on the front, on the tab next to one of the mounting/adjusting screw holes. I'll try to get a picture posted.

Joe,

Just like Tim said, you should be able to find an A or B stamped on them. A couple of mine werent stamped, so the only way I could figure it out was to install them and hold a headlight (low and high beam) in place. You'll know which one is which because if you get the wrong headlight in the wrong bucket, it wont sit "straight". This was pretty easy for me to determine since I had the T-3 headlights (I used the triangle as a reference point).

Thanks for the info guys! I guess I will need 2 buckets since one of mine must be for another car. My buckets are pretty rusty, and I dont see any letters on them, so I guess I will have to install them and see if the lights sit properly. Whats the difference between a high beam bucket and low beam bucket? Do the bulbs have different "alignment notches" built into the back of them? Thanks for your help! Joe

Yep that's right. The alignment notches on the high vs. low beams are different.