Yet another post on the beaten to death subject of the 67-72 4.10 pumpkin swap into an AD...bear with me.
At the junkyard today I ran across a '69 or so
1 ton C-30 chassis and cab with Open Road frame mounted camper body. Looked like a cool rig in it's day, by the way. It is a factory automatic truck. What are the chances of this having 4.10s?
The tag on the inside of the glove box was painted over, so I couldn't get any info from that. It didn't have rear wheels on it and was sitting on the axle. I couldn't turn the axle to try and count pinion/axle revolutions or pull the cover very easily to count ring gear teeth. Plus the yard was closing and I had to leave.
Maybe somebody out there would know if there's a good chance on finding 4.10s in this thing because it's an automatic? If so, I'll probably go back and pull it out.

Steve

'49 3800
'52 3600
'57 3100