If you want to turn the 78 into a show truck it does not sound like a bad deal. If you want it as a everyday driver, for $5,000 you can get a nice Ford truck that is at least 20 years newer, with a much better ride and many more options. I just traded in a 1999 f-250 XLT 4X4 light duty for $4,000 miles for a new superduty. The 99 was a great truck with cap, bedrug, skidplates, 4X4 with electronic shift on the fly, limited slip rear axle, auto headlights, anti-lock brakes, air, power windows, locks, curise, tilt wheel, cd player, power seat, clean cloth bench 5.4 liter with 146,000 miles, that did not burn any oil in 2,000 miles. It was purchased new and very well maintained, oil changes every 2,500 miles and trans changes every 25,000 to 30,000 miles. Never a trans or 4X4 problem with over 25,000 miles of towing apprximately 7,000 pounds.
Just something to think about, the quality and extra's of a newer vehicle, vs the styling and collectability of an older vehicle. If it was going to use it as a everyday driver, I would go with a newer truck. Just my two cents.
By the way, the new V-10 XLT superduty is absolutely the best truck, that I have ever rode in or driven.