zf s 5-42 transmission gearswap

i have a zf s542 5 speed manual trans which came out of a 91 f350 dually with a 460 engine. my inquiry is this...i have to replace gears in this transmission and happen to find different teeth gearing available for this transmission on certain gears on the mainshaft and certain gears on the countershaft.. i plan to use this dually as a street truck and have no intention to tow with it.(not a fan of the low granny gear)... has anyone done any gear swapping between the close and wide ratio and deisel transmissions to change the way the transmission acts and performs..can i mix and match gears and change ratios.. meaning is it possible to change the gearing for street aplications.

Is taking yours out and counting teeth out of the question? The trans will be theoretically the same ratio as yours. Swift it through its gears and count revolutions in to revolutions out to know what it is. If you don't want to tow I wouldn't jack with mixing and matching both the desired result won't happen, or the resale will be zero, or both... If you want to make the other one match yours, lookup the tag number and see what its ratios are. Drive to driven division makes out ratio.
click for service manual (http://www.zf.com/media/media/document/corporate_2/downloads_1/usa/lcv_3/S5-42_47__47M_Service_manual_.pdf)

thanks for the info. i have this transmission totally apart..found that the previous owner liked to slam and force the gears into place all the while having a bad clutch with just barely enough travel to switch gears..most times... This trans would grind between 2 and 3 on cold starts and cold days and not so much when got hot. upon opening the case and inspecting, i found the shift forks severely ground into the synchro gear on the gear itself.. the synchro rings surprisingly werent damaged but are worn from the many years of abuse. I was just curious as to changing the gear ratios to make it more streetable. resale is out the window and i bought this truck because it was huge, loud, and extremely obnoxoius on the the parkways. again thanks.