Saginaw SG's are pretty collectible, a step up from regular Inland Div. (both are GM companies). Your custom stock may not appeal to everyone, but if the rifle itself has not been altered much to fit the custom stock, then a regular GI stock and handguards may be easily re-installed, restoring it to issue condition. It would be hard to value it without good pictures, and knowing if the internal parts have been removed, swapped, or replaced. I have an DCM issued Saginaw SG, and I feel it is worth about $700 or so dollars, in vg-ex condition, with some ordnance replaced parts and M2 stock.