The brand of scope shouldn't matter. A .270 is a .270. I'd be thinking 3 to 9 or 2.5 to 8.
Don't know for sure, but it looks like it takes a proprietary mount. Not likely to be still made.
Try these guys. They seem to be the only game in any town.
https://www.newenglandcustomgun.com/...ts.php?cat=279
Don't think this will help even a little, but it's info.
https://www.chuckhawks.com/mannlicher_1961-MCA.htm