Means it's an RB block, used for 413 and 426 wedge motors. Your engine, based on that and the stampings from the pad by the front of the engine, is a 1965 model year 413, assembled January 20 of 65.
Based upon other tidbits (tach drive diz, air cleaner), you may have a very special motor there.
Somewhere on the engine will be the casting date - there's the same number on both sides of the engine, so try the other side to see if you can come up with the casting date - it should look very similar in location to the pic of the red motor in one of my previous posts.
Based upon other tidbits (tach drive diz, air cleaner), you may have a very special motor there.
Somewhere on the engine will be the casting date - there's the same number on both sides of the engine, so try the other side to see if you can come up with the casting date - it should look very similar in location to the pic of the red motor in one of my previous posts.