Need the SA LH M70 first...
The WSMs were short action, therefore that part isn't a problem.
Forgot about the short mags. Was thinking about .473 bolt face. Can't recall ever seeing a LH SA M70 in a non-magnum chambering. Did they make/sell any ?
As we've discussed before, yes, Winchester/USRA's "custom" shop offered them prior to the 2006 closure of the New Haven facility. Someone had a "custom" shop-produced left-handed Model 70 in .308 WCF on Gunsamerica in 2005 for a cool $2500.
As has also been pointed out, the MRC actions are just bastardized Model 70 knockoffs.
None of this is new information.