The twin shock swingarms should fit and the forks should fit if the CRF70 uses 41 mm O/D steering bearings ...
I know a guy who bolted a stock pitbike swinger straight onto a stock XR75/80 twin shock frame to convert it over to monoshock ...
I don't know about the '84 on model Pro-link XR/CRF 80 rear ends though ... but the forks are the same bearing size as the earlier models ...