If you hadn't brought it up, I wouldn't have thought that option 1 could screw up the oil pump. Is that a strong possibility? Because option 1 is the most labor efficient (as I see it).
Option 2 seems best if you really think that option 1 would screw up the oil pump. With that typed I am assuming that you intend to fill it, spin it, and not just let the mix sit in it.
Option 3 sounds like a lot of work. . . .
Option 4? If it was running okay, with the exception of the vacuum leak through the plenum, you could just buy the plenum repair kit and put it back together. It would probably still go for a long time. . . .
Option 2 seems best if you really think that option 1 would screw up the oil pump. With that typed I am assuming that you intend to fill it, spin it, and not just let the mix sit in it.
Option 3 sounds like a lot of work. . . .
Option 4? If it was running okay, with the exception of the vacuum leak through the plenum, you could just buy the plenum repair kit and put it back together. It would probably still go for a long time. . . .