Also, what was the OG? That and the volume you're fermenting are the important factors. You can figure out carbonation volumes from that. Sounds like ya took RDWHAHB a tad too seriously with this batch, eh?
Well, actually, the two things you need to know for carbonation are the volume of beer, and the current temperature of the beer. The colder it is, the more CO2 it will store in solution. I'd love to help you on an exact calculation, but I just use the carbonation formulas in Beer Alchemy.
You need the gravity readings to make sure the beer is finished fermenting, but I really don't think they will come into play with CO2.
My advice is to find a calculator that takes temperature into consideration for priming rates, and round down on the volume you expect to bottle. In other words, you may see that there is 4.25 gallons in the primary, but at least 1-1.5 qts of that is yeast and trub, which will be left behind. It would be safer to use 4 gallons for calculation purposes.
Bottle conditioning is actually a tricky thing, because you really only have one shot to get it right. If you just want the beer to be carbonated, then ~4-5 oz of sugar will get the job done, but if you are trying to get an exact and repeatable volume of CO2, then there are other factors that need to be considered.
Joe