The major considerations are how to get her Home!
Pretty sure JBC is dead on, definitely looks like a Chieftain 25. And she got the custom chop top job. Now I'll say up front that I have a Chieftain 25 so my opinions are definitely biased...
A lot of people seem to only like center consoles/no cabin setup and remove the superstructure from these good old boats. I bet it was a Chieftain 25 "Express" originally, floor in back looks deep. I'll find a picture. If so- it had a cabin and two levels of big glass windows wrapping around. The 25 models are more rare so there are less pictures and videos of them floating around.
The later models like that '78 should have the nice rib end reinforcements from the factory that some earlier models did not. That's definitely a big plus! It is a significant strength upgrade and prevents cracking in severe use at the rib ends.
The rivets can definitely loosen over time through rough use, like any riveted aluminum boat, so that is definitely something to inspect. You can tighten up (called "bucking") a few loose rivets here and there but probably don't want to be bucking dozens and dozens, depending on price and your dedication to it. Personally I think they're great, light, low maintenance hulls that are super easy to customize. That one looks like it was setup kinda like a pontoon or tour boat.
This is an outboard powered boat you say?? (may have misread)
My main concern would be how the outboard is mounted. These babies didn't have an outboard option ever for the 25 that I am aware of, you -could- get it brand new without any inboard installed but it wouldn't have a splash-well or notched transom or anything. Could have been very well converted but my attention would be focused there. I saw a build where one was outboard converted with an offshore bracket and it looked great. Interesting boat for sure, have any more shots of it?