The neoprene works well. I did have a problem with them in my 1955 235, but some silicone on the outside solved that.
You should have no problems with your late model, probably no silicone needed, just follow the instructions that come with the seal.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-