I can get you some 8-track tapes. Not cheap, but it's easier than finding one of those gizmos that allowed the use of a cassette tape. Hmmm. It'd be funny to have that, in use with a 'cassette' adapter so you can play your iPod....
I've bought 8 track tapes at thrift stores for as little as 25 cents. They're typically $1.00 at auto flea markets/swap meets. It's a gamble as to whether they work or not, but the odds are better than for a $1 lottery ticket. I just searched 8 track cassette adapters on ebay. 133 listings. If you want to pay a little more and avoid doubling up on adapters, you can have someone wire an 1/8" headphone jack directly into the radio/tape player. I think there are also adapters that can be plugged into the antenna jack. Note that by 1980 Ford also offered an AM/FM/Cassette for this car. The radio/tape player chassis were pretty well standardized at Ford by this time, so it's very probably an easy swap. The only drawback is that these days it's not much easier dealing with cassettes than it is with 8 tracks. Car looks pretty nice for the price, but remember, it's Canadian and may not have AC. It might also have the VV carb (great gas mileage when it's set up right, but not many people can do this; also cores are expensive, rebuilds very expensive).
If I'm not mistakin' - All these wagons were built in Ontario Canada for export to the US. This one, like most of them, does have A/C. It may or may not work, but it's there. You can see the labels on the climate controls in the photos of the add.