RJ - make sure to take lots of pics & post a writeup on bulltear. Let me know how much grinding on the case you have to do to get everything to fit.
I acutallly bought my 18 8 37 EB D20 gear seperate for $25 and didn't have to find the entire case. I got the D18 gears from a shop that had some already disassembled gears so once again I only bought the gears and didn't have to ship the entire case. I know that you can tell the difference between T-style & J-style EB D20 by looking at the case/shifter. I will look again to see if I can find an exact way to tell. I know that the T-style was in '66-72 broncos and the J-shift was 73+. Also, I think that the later J-style had a higher 4low ratio (more like the jeep D20 2.03:1). If you count all of the gears, you can calculate the 4low ratio - if it is 2.46:1 then it is definitely an earlier T-style case.
I am still not 100% convinced that the 18 8 37 is the same as the 18 8 58. I talked to my jeep expert (he parts out jeeps for a living and has always given 100% correct info before), and we both feel pretty confident that Spicer didn't put different p/n's on gears that were identical - something is different about them. - who knows what it is though...
As for gear pitch off of novak - I think that you are right that they are talking out the angle of the helical gears (duh - why didn't I think of that
) .
However, there may still be differences in gear pitch/angle of the straight teeth. The curved/rounded portion of the gear tooth itself can be different between gears. This curve must be matched between all gears so that the teeth roll on each other instead of sliding. If the gear teeth do not mesh correctly and slide instead of roll against each other, wear/friction/noise will be dramatically increased. I was planning on digging out a couple of my Mechanical Engineering books from back when I was in school and doing a bit more research on the subject.