As has been said above the oil seep is probably the pucks under the cam towers from the lack or running and shrinkage of the pucks. It isn't usually the head gasket.
Sometimes the pucks will swell back from running on a regular basis. Someone wrote of rolling up a sheet of paper towel into a tube as a diaper to catch the oil as a temporary thing, clean out the oil stains with brake cleaner and paper towels, then stuff the diaper in the fins just below the head while cycling heat and cooling of the motor to get the pucks to swell back to sealing.
I did it on my K5 when I brought it back to life successfully. I would do it on a pristine bike like you said it is before pulling the pucks out and replacing.
As to the holes in the mufflers, yes it is common from not riding any exhaust in any temperature long enough to burn the condensation out of any motor and exhaust. Many people wrongly think they need to run their bikes during a winter sleep for a few minutes to circulate the oil and the gas in the carbs or to keep the battery up. That does more harm than good, especially to the exhaust systems.
Finding good 750A exhaust to replace them will be a hunt that will take lots of time....
But, if the holes aren't too bad they might be able to be cut out and make stainless steel patches to fit the cutout and tig welded in, then buffed to look like the chrome. There's a guy on fb that did a nice job on some 500/4 mufflers a year ago. Before seeing his postings on it, I had patched a friend's 750 mufflers making sheet steel patches over the outside of the holes and having them tig welded then painted with high heat paint. So far they are holding up for him and sounds good now.
