Were optional rear ratios listed on the trim tag?

[jayoldschool]

Wondering about the rear gears in my 65 C10 230 3spd. Research so far has turned up that 3.73 was stock, 3.07 and 4.11 was optional. Found the code for 3.07 on another thread thanks to this pic:



I see that the economy option got a different carb, too. Any guesses if this is that setup? I don't recall seeing this air cleaner on anyone else's truck (but I haven't been around here long!)



Here's my trim tag:



I've noticed on other trucks that the tag seems to only list trim and paint. Since it is a 65 with no SPID sticker, is the only way to ID the rear to check for the rear end tag or count driveshaft/tire revs?

I welcome your thoughts!