I haven't used them, but I've been told the Best Gasket neoprene seals (black in color) are not as good as the ones made by Fel-Pro for decades (the orange ones). Fel-Pro stopped making these about 5 years ago and the seals and friends familiar with both say the orange Fel-Pro ones last longer. I can tell you no matter which you choose (rope or neoprene), polish the crank surface very well. If a rope seal was used originally, the seal will be pock-marked and rough. I don't know if the neoprene seal was ever installed by GM when the engines were built. When I was young you had to have this installed by the dealership (if you had the right engine). Another good idea is to install a Speedi-Sleeve over the rear part of the crankshaft. Good luck.

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