I love this site too!
The tag thing is good. Hope the 91 still has the tag. I became an expert at the count thing because the 1981 F250 4by I used to have seemed to take 6 grand RPM to keep highway speed on a good solid C6 trans. I knew they did tags, but my old truck had no tag. Since I knew all the gear ratios those vintage Fords could have- I rolled the truck by myself on my driveway and was absolutely positive I had 3.55's, not 3.25's or 3.72's. Finally though, I broke down and pulled the differential cover (I needed to chage fluid anyhow). When I counted ring and pinion teeth- I found I was dead nuts on- 3.56. I have also seen tags with a bunch of coded crap only on them. Reading tags IS quicker than the roll thing (tags are very precise but also only as good as the dude who hangs them, hardcore physics doesn't lie- have fun- yeeeeehah). By the way... Its pretty tame. I actually spun my driveshaft turn by turn with my hand, which caused the truck to slowly roll forward as I counted.