gear ratio's direct drive emaxx tranny

[sly118]

hi there , ive converted my UE - maxx to a direct drive centre gear from a ofna 1/8 buggy but now im stuck with matching a gear ratio , please help with suggestions , currently got 9L with 20 pinion and 66 spur and that was sweet , centre diff has 46 spur atm but ill have to wack a 51 tooth plastic spur on .. but what pinion ?? also have to keep in mind the ratio change from the tranny . b4 it was 1.75 turns of spur = 1 turn of output shaft , but now its 1=1

please help ?? mike ? any ideas ?