Thick or thin cab bushings?

[72truckster]

I have searched for an answer but cannot find one. I got a new set of rubber cab bushings with my truck. So I want to give them a try. However they are a different thickness. Are they supposed to be? also Im sure they are not for the rad support. So can anyone please tell me if the thick ones go to the front or back of the cab. It is a complete frame off resto, so I would like to get this right before the doors and fenders go on.

Thanks.