Up for sale as a package at Mecum Kissimmee. The wagon has 59,000 miles. They don't say anything else about it other than that is the 307 engine. The bidding reached $17,000, but it was not enough to meet the reserve, so "the bid goes on." You can go put in a bid right now. https://www.mecum.com/lots/FL0119-356112/1990-oldsmobile-custom-cruiser-wagon/
I had the same thought. Why tie them together? I'm sure the market for the wagon alone and the trailer alone is much larger than the market for selling them together. By making whoever wants the trailer also buy the car or whoever wants the car also buy the trailer, you greatly reduce the number of potential buyers.
Personally, I like the probably not stock woodgrain. The front seat belt anchors thanks to G.M. Loophole engineering, though? No. (And yes, this car is still stock in that regard.)