Installing small block from the bottom

So the engine, k-member and transmission are in finally. Here is what was done. We found (like others have said) that there is a variation in Pitman arm sizes, even when they are the same part number. So we found one that had a hole .120 inch larger. Then cleaned the splines real good on the steering box, which wasn't done by the rebuilder. Don put that on and we then had visible thread on the bottom of the gear box shaft. Then loosened up the motor mounts and rocked the motor to get it at the very bottom of both ends of the mounting hole. Finally (and this is probably the issue in the first place) we lowered the tailshaft of the transmission when we finally realized that it might be higher on the test stand than it would actually be in the car. We got adequate clearance at that point and lowered the car onto the engine, tranny, k-member assy. Thanks for all the comments and suggestions.