Brake drum question.

[Russell Ashley]

This has cost me several trips to the parts store and a day of lost time. My truck has a 12 bolt rear with the numbers 389486onf cast into it. It also has GM55 and A230 and CON1 cast into it at different locations. If there were ever any stampings on the axle tubes it's gone now so I can't tell what it originally came in. This was originally a four link rear. It has 11 by 2 inch brakes, with 5 on 4.5 bolt circle. The problem I'm having is finding drums for it. It seems that all of the 11 inch drums have a 4.75 bolt circle. I've searched the internet but can't find any real specs for drums that give me the dimensions. Can anyone shed any light on what GM 11 inch drums would have a 4.5 inch bolt circle. My truck has Corvette wheels and the disc brake kits I have have the 4.5 inch bolt circle so apparently this was a size that GM used at some point. My parts guy is being very helpful with this but his computer doesn't show the bolt circle, just the shoe size.