Driveshaft carrier bearing flange bolt size?

[Zenwren]

I've got the driveshaft from my 69 C10 LWB taken apart and discovered that a previous owner totally buggered the threads on the big bolt that keeps the splined flange on at the carrier bearing. Can anyone confirm the size of the threads? I'm going to try to chase them out and hopefully get away with just replacing the bolt. It looks like a 1/2-20 but mine looks like someone took a grinder to it and just ran it home with an impact.