Polytech/Norinco is an excellent rifle,forged receiver,forged one-piece op rod,excellent chrome lined barrel etc.But it does have some issues,some minor some not.Minor issues include,gas lock thread is not the same as G.I.,Gas system not chrome lined,short connector lock pin and rear sights are a crap shoot.Some are fine some are not.The only major issue is that headspace tends to be long and some bolts are soft which can become dangerous.Most people err on the side of caution and have a G.I. bolt fitted.I would the check headspace,if it's ok then record it and recheck every couple of hundred rounds or if there are signs of excessive headspace.When/if it becomes unacceptable then have a G.I. bolt fitted.Any M14/M1a stock will be fine BUT,the connector lock pin on the poly is shorter than G.I..You can either glue in a popsicle stick or some bedding material to keep it captive in case it walks out or replace it with a G.I. pin.The G.I. pin is both longer and about .005 thicker . Out of curiosity,just how is it you have a Winchester M14? A pre-86 NFA?