If the engine is healthy compression wise, valves, guides, etc...I say go for it. I agree, the earlier pre-smog Olds 350 is a ballsy power plant. A friend of mine had a '69 Cutlass S back in the day, and that car moved along nicely on the open road.
As for the headliner, Be very gentle and patient removing the headliner. The backing boards can be quite brittle.
You'll have to remove the sun visors, dome light, and the perimeter trim that essentially holds the headliner board up. As you probably noticed, the wagon headliner is in two sections. Be careful removing the perimeter trim, the clips break very easily and the rear trim clips(over the rear hatch glass) are very difficult to find.
It's pretty straight forward, just proceed with caution. When the board is out of the car, inspect it for cracks and fractures in the styrofoam. You can always use fiberglass matting and resin to make repairs to the board.
If you're experiencing any problems, just holler.