140 speedo question

[69L72RS]

I called about a 12-bolt rear that was advertised last night and found out it is still in a rusted up 68 body. I asked the guy the usual questions about what was left on the car and what options it had. Not many options just 12-bolt, 4-spd, and a 140 speedo. A 140 speedo means it is possibly a Yenko, right? Did any other cars get a 140 speedo? I am a little confused because he said it doesn't have a tac. Didn't all Yenkos get factory tacs?
I'm going to look at the car tonight. Is there anything special that I should look for? I don't know that much about the early Yenko cars.