Several days ago I was asked about removing the clutch assembly and I did not have available, the correct size of the bolt I use to remove it. It is cad plated, 5/8, x 11 coarse thread. Threaded portion is 1 3/4" long with a non threaded portion of about 3/4". So total shaft is about 2 1/2 inches long. Could be a little shorter so it will clear the fan and shroud if you need it to be shorter. The hex head of this one is 15/16th. I got it at a Pep Boys so it is easy to find. This is installed inside the center of the clutch assembly after the small bolt is removed from the same hole. Its threads are further inside and are in the crankshaft. This larger bold grips the cluth itself and pushed against the crankshaft. This is the same on all the cars I have from 59 thru the late 80's and are the V2 compressors. I do not know anything about the rotary compressors. Joe Machado The dual air in my 61 LeBaron works awsome. It has hit 120 so far here in Palm Desert.