Before you install the oil pan, take your time to check and be sure the seal is making contact with your crankshaft--all the way around. I mention this because my 1959 235 wasn't and I had to shim the seal on the rear side by about .003. Also make certain the portion of your crankshaft which will contact that seal is smooth. If it is pitted and rough, you won't get a good seal with the rubber seal and it will wear out more quickly. That BEST seal is pretty costly. If you want to buy one of the Fel-Pro rubber seals, please contact me. I bought some when they were still available. At the end they weren't cheap, but less expensive than the BEST seal and do the same job. Also check the clearance between your rear main bearing and your crank. Regardless of which seal type you use, you don't want your crank moving around any more than it has to.
Jon

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end