You should be able to get the top part of the neoprene seal out without dropping the crank. Have you tried pushing on one end to see if it will rotate out? Just asking, because a lot of the guys here seem to be inclined to replace the better two piece neoprene seal with a new rope seal.
Was the neoprene seal leaking because it was installed in a motor that was not machined for a two piece seal? For example, the 56 235 was the first year for the neoprene seal and the 55 and earlier blocks cannot be retrofitted because the machining on the rear main cap is too deep for the two piece seal and so you have to use a rope seal.
The other thing is that the rope seals of yesterday had an asbestos component to them. Today’s rope seals are a fiberglass graphite and do not work as well and are prone to leaking themselves. Not every Installation mind you, but quite a few.
If your block is machined to accept the two piece seal, which is an improvement by the way which is why gm switched over, why are you going back to a rope seal? No criticism here mind you, just couriosity.
