I hate to bring back the dead <img src="/forums/images/graemlins/zombie.gif" alt="" />, but I was doing gear reaserch and I think you have your calculations wrong...

if

(stock transmission X stock diff X stock t-case X 336 X MPH) / stock Tires (inches) =stock RPM

and you want to keep it that way or as close as you can, then:

(transmission X stock diff X t-case X 336 X MPH) / stock Tires = (transmission X New diff X t-case X 336 X MPH) / New Tires.

so, if everything else stays the same it croses out... and if you are running 5.29, this ecuation should give you the new tire size to keep as close to stock as you can:

4.625 / 29 = 5.29/ New Tires --> (5.29*29)/4.625 = New Tires (33") give or take .2 inches <img src="/forums/images/graemlins/notooth.gif" alt="" />

if you also changed your t case guears, just include them in the ecuation (multiply by [new t-cas/stock t-case]) <img src="/forums/images/graemlins/kewl.gif" alt="" />

anyway... I think my SWB genII has the same drivetrain setup than the 89 v6 3.0 SWB, how to be sure though? just mesure axel heigh? 8" and 9", right?