help picking a speedo gear...

I need to order a new gear for my coronet.

4.10's with 27" tires.

http://www.moparts.org/Tech/Archive/auto/12.html

Is there a better chart some ware? Im thinking just a 40 or 41..but want to get the closest to right one.

I get an orange 40 tooth (39.773) from here, Chrysler chart is at the bottom - (use 13 drive teeth)

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

Great link. Thanks.

OK who the heck sells them? TCI says they are N/A.

EDIT: Never mind. Found a moparts sponsor that does..

I followed the chart after putting a piece of metal stock on top of one of my rear tires & getting my ACTUAL diameter. Made my odo spot on(checked it out on the mile markers on the interstate) & luckily my speedo also became correct(measured at a digital road sign) as the magnetic gismo in the speedo can be off even if the odo is correct(ed) with the right speedo pinion but the right tooth speedo pinion has to be taken care of 1st & if the speedo is still off the speedo head needs to be taken into a speedo specialty shop & recalibrated.

Well as long as its somewhat close i'll be happy. Right now ive been running the gear for the 3.23s and its way off.