I would get 73", It's better to get a measurment higher than it reccomends, just because if it doesn't fit, you have a extra lenth.
if it doesn't work, take it back, and get one custom made.
Also, you can cut it to size as well.
Thanks for the reply! Yeah ive been doing home construction for a while, so I know, but sometimes, I need a little help in certain areas, especially doors.