The wagon looks like a nice car for the $5500 asking price, if fairly low option other than the 400 V8. What strikes me odd about it is the Snowflake Wheels it has on it. As far as I know all Full Size Pontiac wagons from 77-79 all used 5X5 Bolt pattern Wheels? And as far as I know aa 15" snowflake Wheels used the smaller 5X4.75 Bolt Pattern? https://albany.craigslist.org/cto/d/new-baltimore-1978-pontiac-catalina/7041648063.html
They certainly look good.... Easiest way to change the bolt pattern would be to swap out some parts...….. A lot depends though on how far you have to go to get everything working together. Does swapping out the front hubs mean you have to also change the front rotors and calipers? The wagons probably had slightly bigger brakes. And does swapping out the rear drums mean the entire business end of the axle needs to be changed?
I have been thinking about it, I am now wondering if you could just swap out the front rotors, and possibly swap out the rear axles from a 77 A-body wagon? They also use the 8.75 BOP Axle that the 77-79 B-body wagons use. I actually have one laying around from the 77 Century wagon I scrapped out years ago. HMMMM If not the rear axles could be redrilled for the smaller Bolt pattern, Or the wheels Modified for the larger Bolt pattern is More likely.
I agree that is a way to do it, but they will move the wheels out the thickness of the adapters usually 1" or more per side. so unless you are installing custom offset wheels the wheels will be moved out 1" per side. The wheels in the pictures seem to sit in the same location as the ones on my car with 15X7 plain steel wheels. My Car on top, cat from add on bottom.