None are insurmountable but the unwary can soon fall into a trap that turns into a chasm. And one that you can get into, past the point of no return VERY quickly and end up with a pile of tat.
Last year I collected Repro pads and mount and have a suitable donor rifle that already has been drilled and tapped for a aftermarket scope mount. I have plugged the old holes and I'm ready to drill and tap for the repro pads. Next hurtle is BA taps and mounting screws.

I'll be watching for more info on this..