That 50 or 60 miles probably means a two hour trip. I would be reluctant to go late in the day or on a weekend when the dealer's staff would be busy, but during the day on a weekday shouldn't be a problem. Don't tell the salesman just how long or how far you expect to go, but rather that you'd like to take a test drive and do it. Then be convincing to the salesman so he's not encouraging you to return to the dealership.
I've never taken a test drive that far or that long in anything I've bought. My test drives have all been in the 20 minute range, but that was enough for me.