Pennzoil:
British cars are relatively easy to get parts for in the US. There are three major sources of parts for these cars and many minor sources. Austin-Healeys are more rare than MGs and Triumphs, but parts are still available. In the US, you can get nearly any part you need within a few days.
I'll have to look into it, but I don't think "Austin Rover" existed in 1967. Austin supplied parts for Austin-Healey vehicles, but "Austin Rover" wasn't created until the BL name was eliminated about 15 years later.