I also found a '36 LB engine WITHOUT the LB marking on the intake surface. Removing the pan is the best way to tell. The LB mains stud distance center to center measures ~ 3-1/4" while the poured babbitt mains will measure ~ 3" C-C. The oil pan will be slightly wider at the front main but I would not rely on this method alone to determine if engine is LB. After Ford widened the front of the oil pan I'm sure they also used those pans on non LB engines. Plus someone could have put a widened pan on a poured babbitt engine. The best methods are not always the easiest. Remove the pan, measure the distance between studs, and then remove a main cap just to be sure. JMHO