The car is being discussed in this thread: https://v8buick.com/index.php?threads/1967-buick-special-rust-free.393568/ That post shows different numbers than what you described. Vin 43517..... Data plate is 43617..... The difference would be V6 vs a V8, as shown in Erik's post:
Don't get me wrong... it is a very solid body but does appear to be a V6 Buick Special Deluxe(according to VIN) and should probably be treated as such. It appears to have a fairly complete 300 2bbl in it.
They are nice solid cars. If the price is right go for it! I would not be put off by the engine swap.
