The 2 valve Ford V10 is a solid motor. Very few issues but they do tend to blow out their spark plugs. It can be fixed if this does happen, but it is usually a mechanic with special tools procedure. 150k is fine for this engine if it's been maintained. Maintenance is vastly more important than a mileage number. My van has almost 300k on it and I'd drive it across the country without a second thought.

Heads up on fuel mileage. In low roof config like that, you are looking at about 10mpg, a high roof might drop that down to 8 or 9 mpg. Not a big deal if you are parked most of the time, but if you are planning on big miles it can be a significant cost vs something that gets a bit better mpg.

And as others have said, pay for a mechanics inspection.