I think that if an engine is designed to have a rope seal, you cannot use a rubber seal as the block/cap are not machined true enough for the rubber seal to seal perfectly when the cap is shimmed properly and torqued down.
Also, Best Gasket rope seals come with a pin (to keep seal from rotating with crank) that you drill into the cap (and maybe the block, cant remember). So, maybe someone installed a pin in the block and that is why you cannot push/pull the new seal into place.
