I would use the gray silicone on the main caps, Don't put thick coat of it, Just a very thin coat, It will come out and not change the clearance. Rope will seal most anything, Its wider on the contact to the crank. If there was some ware on the crank area where the seal rides on the the crank the rope will fix that,Rope seal needs to be fitted tight and to do it on your back will be not easy but can be done. Trimming the ends of the rope is the key,Sharp razor blade a must, Your engine will turn over harder but once the crank spins it will get better. Getting the seal in the block side is tricky,you can get a tool for this at parts houses,the next best thing to do is loosen all the mains caps so that the crank "drops" a little and slid the rope in and once it's in tighten up the mains before you cut the ends of the rope seal.Take the cap and put it in your vise and install the rope and use a round tool to roll it into the groove and then cut the ends on that,RTV thin coat on the cap and install.

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