Petmil,
My personal opinion for additives to rejuvenate any seal is this:
They "might" work to soften up the neoprene seal and help things along for a short time. They won't fix the problem. I don't think an additive is going to do squat for a rope seal.
I wouldn't believe the rope seal is never going to seal adequately. Since you just had your engine rebuilt, that might be the testament for my last remark.
I don't know how you are ever going to rejuvenate a rope seal. I think they would be very hard to get out, and more so going in, without pulling the crank. I have never done it with the crank in place, but rope seals are in there pretty tight. Some are anchored with a pin also. I would think that would be hard to deal with also.
On the V8 engines, the neoprene seal replacement will ride on a new surface of the crank (I cannot claim the same for the 6 cyl.) and not on the rope seal surface. The rope seal surface of the crank is usually pretty worn and that surface is not used with a neoprene replecement.
If I were going to replace the seal with the motor in the truck, I would DEFINETELY go with the neoprene at this point.
