I can't speak about the Lincoln air suspension, but can give you some info about hitching up with the air suspension we have (on a MB GL320). Ours is fully automatic, meaning that the computer will try to level up the vehicle no matter what load is in it, and it cannot be turned off.
We started by weighing the tow vehicle with our normal passenger and fuel load (full tank, three passengers). This gave us a baseline weight for each axle.
Initial hitch setting is done with the engine off and the suspension in the normal driving position. We measured the corners of the vehicle before and after hitching, and adjusted the hitch until the vehicle "drop" was approximately equal. This is standard practice for weight-distributing hitches.
Then we started the car and let the air suspension level the vehicle. Next step was to take the rig to the truck scale again to get new weights for the axles. These were compared to the Gross Axle Weight Ratings and the "normal" weight ratings taken earlier. We adjusted the hitch again slightly to optimize the axle balance, and then we were done.
Later we took the vehicle to Can-Am RV to have the hitch strengthened (I've seen too many cracked OEM hitches!) and optimize the Hensley a little further.
There is a myth out there that air suspensions "destroy" the weight distributing ability of a hitch. That is untrue in regards to a modern computer-controlled 4-wheel air suspension. It may be historical knowledge from the days when people would put stiff air bags on the rear suspension, to "level the vehicle." That practice can disguise an unbalanced load and potential handling problems.
With any air suspension, you need to weigh the setup to know for sure what load you are putting on the tow vehicle axles, since you can't just "eyeball" or measure the way the vehicle sits. A modern air suspension will level up the vehicle regardless of how unbalanced the load is, and this can lead to a false sense of security.
A '71 Safari or any 1970's Argosy 24 have about the same tongue weight. Expect at least 600 lbs, and possibly as much as 800 lbs. That's a significant amount of tongue weight, so take your time and set your hitch correctly.
You should definitely read the article in the Spring 2010 issue of Airstream Life
by Andy Thomson about hitching. In my travels I see more incorrectly hitched vehicles than correctly hitched vehicles, and for that reason we're running a series of articles on this very topic.