I drove 65 to 75mph for eight to twelve hours a day for two days from Cincinnati to Houston in my '85 1.9L automatic.  My engine has just over 55K miles on it -- no rebuild. The tach showed 3500-4100rpm which is within the green range -- 4100 gets into the green fringes.  Shouldn't be a problem as long as your engine is otherwise healthy.

Chuck
'85 Westy Weekender -- 'Roland'