I love it!

You hardly ever find those things today. It is presented as being a survivor. To carve that thing up is sacrilege. Besides, if it was turned into a pro-street LS 6-speed (cool as that would be), it would then get resold State-side and another Canadian hybrid Pontiac lost from Canada. Wagons are rare to begin with, though I remember a clean light blue '66 Laurentian wagon near me in the seventies that was traded in on a new '75 Parisienne, and another mint '66 all-red Laurentian wagon (belonged to a friend's uncle) that was traded for a new '75 Malibu Classic wagon. It almost seems like the time to score a decent survivor wagon at a decent price was 1975!

The 250 was new that year & had more counterweights than the then-current early 292 six. A good engine for a tractor. Anyway the big car wagons with six cylinders came with 3.55:1 ratio out back.
Leave that car alone, just perform tune up & maintenance, use as intended and it should be decent on fuel. Try to flog it (or not) and you will be surprised at how peppy it is - up to a point. They can also deliver mileage in the mid-teens if not tuned up or if the Rochester BV carb needs attention. I would estime 19 or 20 mpg realistically, but then again I expected 19 ~ 21 mpg out of my Chevelle 250 Pg with 3.08s & managed 30!

Come to think of it, the LS 6-speed with updated brakes that require large wheels, perhaps like cdnpont has on his '67 GP sedan, would be super-cool.