That's just what the Mustang needs..... a real long road trip. You will be surprised how much better it will run after the long trip. When I first got mine ten years ago, I drove from Texas to Maine and back. I still drive mine on long trips. A good 70 MPH steady speed won't hurt that engine at all. Take extra parts and tools with you.

 

So long as your car doesn't have any overheating problems and you take tools like was suggested you should be fine. These cars are definitly capable as long as it was restored alright, hell my 68' I drove from Phoenix to Cincinnati when I first bought it (3 days of 10+ hours in a row) then did Cincinnati to Detroit and back several times, Cincinnati to Nashville and back for the 40th anniversary show, and countless 1-2 hour trips. Truckers love the classics too and whenever I do trips in my stangs they seem to be alot more considerate. That and you always get the gawkers and people talking to you about the car everywhere you stop which can make the trip much more amusing.

The biggest reason I like to use my stangs though is because mustang seats I find even more comfortable on long trips than modern cars!

Now on the flipside there is always one last thing to consider... do you have a music system you can stand to listen to for that long?

 

I would put some highway gears in it, make sure the fluids, belts and hoses are in good shape, and spring for a new set of tires just because new tires are cool..

I have driven old cars long distances like that ever since I started driving. Only got an EFI car when gas prices went over $2.00 because 30 mpg is better than 18-22 especially when you have reclining seats and working AC..lol.. But I would still drive the 70 GTO that distance, because I rebuilt everything in it and I can fix almost any of it anywhere, not that it has ever broken down on me.

If you trust the car to go an hour away, and it has been reliable, then 15 hours shouldnt be a problem. I would do the gear swap just to save some gas, if you dont already have 2 series gears..

 

I trust mine all the way. If you keep your maintenance up and get underneath it once and a while and inspect things you should have no serious issues or any issues at all.

I drove mine on an 8 hr round tip Wednesday with no problems started at 800ft and ended at 5000 ft (then back again) with most of the driving at 65 but about 30 min at a steady 85 to 90 mph @ 3300 rpm no problems at all.

Take her with ya.

Gun