Possible wiper motor problem on my '65?

[nxtruck]

Guys,
I'm wondering if anyone else has dealt with this issue. On my '65, the wiper motor still works ( it's a single speed motor ), but the wiper blades don't stop in the same location each time. Sometimes, depending on how I adjust them, they'll travel off the sides of the windshield. Or they'll slam the bottom of the windshield weatherstrip if they're adjusted too far down. I've looked into the Newport Eng. wiper motor as a replacement, but I'm wondering if this will even correct this issue. Also, would a o.e. type replacement motor from one of the vendors work as a suitable replacement, being that they're $100.00 or so cheaper than the Newport motors?
Thanks in advance for any help!!