I dont have an answer on what the "nominal" length is for your app but what I would do is with it up on stands (stands under the axle not the subframes) so that it is "loaded" then butt the shaft all the way forward into the trans then see where you are at at the pinion end (want ~3/4-7/8" less than the C to C with it butted forward all the way into the ext housing. If the shaft is too short then with it butted all the way forward hold the rear ujoint "squared up" & measure the gap that it would take to seat the 2 cups squarely into the pinion then subtract 3/4-7/8 from that dimention. If the shaft is too long, with it butted forward, square the ujoint up & measure from it forward to where it would be actually seated into the cups if it was shorter then subtract 3/4-7/8 from that dimention.