PLEASE tell me you're in NE Ohio!?
1977 is the cutoff year for smog check. "Check" with the owner if smog check is necessary. Also look at the registration sticker on the rear license plate and cross-reference that date with the amt. of time the Jeep's been on the market. A failed smog check is a GREAT reason to sell (which means you'd have to absorb the cost of refurbishing crappy smog regulatory crap) <img border="0" title="" alt="[Wink]" src="wink.gif" /> .
Bringing a magnet is good; using a key to poke up on the floor boards is better. The last '70's Jeep I looked at (in Cuyahoga Falls/Silver Lake area last week) initially looked like the frame had been dipped in rust-resistant undercoating, but upon closer inspection the owner had spray-painted black paint over the rusty frame (I noticed the overspray on the body lift).
Test drive it
through every gear and every conceivable terrain. Let us know how it goes! How much they asking? Always calculate estimated costs to fix stuff that you encounter and deduct it from the asking price. If you want, post pictures for us to see (and VIN) and we'll help you barter/fillibuster your first epic Jeep purchase!!