The only commonly-available rope seal that's worth the effort to install is the Best Gasket seal. Follow the instructions that come packaged with the seal EXACTLY. The OEM seals that actually worked had asbestos in them, and the tree huggers banned that stuff in everything some time ago.
Doing an in the frame rope seal replacement is risky at best, even with the Best Gasket seal. You'll need to loosen all the main bearing bolts a couple of turns to let the crankshaft drop down a little to replace the upper seal. The Lisle "Sneaky Pete" rear main seal kit is just about a necessity to do a successful installation. The seal is over-length, so you'll need to trim both ends of the upper rope flush with the block after packing it into the groove as well as possible. I tighten the first three main caps a little, and rotate the crankshaft to pack the upper rope into the groove, and repeat that process several times before trimming the rope to length. Once the upper seal is in place, then use something round and smooth to pack the lower seal into the cap. I machined an old 4" piston skirt to the seal diameter, 3 7/8". Once the lower rope is packed in firmly, cut it off about 1/32" proud of the cap- - - - -Best provides a trimming guide and a mini box cutter to do that job. They also send a stainless steel shield to protect the crankshaft while trimming the upper seal. Add a dab of non-hardening brush-on sealer like Permatex Super 300 to the joint between the cap and the block. Retorque everything and install the oil pan- - - - -good luck!
FYI: I've replaced dozens of rope seals in all sorts of engines over the past 50-something years, with about a 95% success rate.
Jerry
