The two piece seal works well if the crankshaft surface isn't scored or pitted.
I've done Best and NOS rope seals in a GMC and several Chevys. Works well if done with the crank removed as mention by Ken.
If not removing the crank you may want to follow the GM service bulletin for rope seal repairs on 80's Buicks and Chevy 2.8's.
Remove rear cap and replace lower rope seal by rolling it in.On the upper seal,use a wood dowel and light hammer to press up the seal ends. Then cut short lengths of the remaining new half and pack them up into the space ( NOS asbestos seal is preferred). Trim the excess carefully.
