You got to be kidding!. In 79' I took a 77 Camero with 70K from Jax Fl to San Diego in 48 hrs, then across Death Valley to Flint MI. 3 days later, then back to FL with no problems at all. That was 35 yrs ago! One big triangle! What makes you think that BMW reliability is so bad? Cars have progressed somewhat since then. Just change your oil and top off the fluids if your worried about anything.
Oh! by the way. You may need an Italian tune-up about half way, that means - floor it for about 5 miles to clean the carbon out!
Report back after your trip.