What was the first year for the SC Cab?
 

I thought 1983 was the first year for the SC Cab but I just looked at one with a build date of 12/81 making it an 82 model year? Is that correct or is it a hack job?

Sounds like a car with the factory Targa-to-Cab conversion kit that was available in the late '80s.

1983 was the first factory offering for the 'official' Cab!

It may or may not be a hack job - there were a lot of dealer cab conversions using factory parts, and the job isn't very difficult for someone with good basic mechanical skills. Only someone who knew what to look for could tell the difference.

Anyone know how much it cost to do a targa to cab conversion?

The big wildcard is the cost of the top, which could be anywhere from $1000 to $3000 depending on your luck. The side mounts are available repro for ~$200. Then it's just labor from there.