advice

about the only difference between 289's over the years si the switch to 6 bolt bellhousings in mid 1965. other than that all 289 heads are the same port and valve wise. the hipo's had screw in studs and cast in valve spring seats.

How long has it been sitting? I'd be a little leery of the situation based on what little info you've given. Switch out an engine to gain 13 cubic inches? You wouldn't even notice it if it were stock for stock. Now if he were replacing it with something more powerful, that's a different story.

If nothing else, pulling your engine to build and putting this one in while your doing that would still give you the ability to drive your car and you could possibly spend a bit more time and money making your engine more like you want it. You could likely turn around and sell the temporary 289 later for what you'd have in it, maybe a bit more.

289s a 289s a 289.