I used to have one that was manufactured by IOR. IOR, steel one-piece 20 moa base including the 0.330" receiver hole spacing. It had an extra hole drilled for that spacing so it could be used on both the standard long action Winchester 70 receivers, and the Winchester Express magnum receiver which has the narrowly spaced holes (0.330") that you're looking for. I sold my IOR base to another member - only because it was steel and I wanted to go with a lighter aluminum scope rail.
What I ended up doing is purchasing an aluminum one-piece rail from Brownell's (about $40) and having a local gunsmith (my brother) drill in the extra hole for the 0.330" spacing. But Brownell's didn't offer 20 moa rails at that time. Don't know if they do now or not. But if you simply can't locate the rail you want with the 0.330" spaced base mounting hole, you could purchase any 20 moa rail for the Winchester M70 long action and do the same. Have a gunsmith drill the extra hole to accept the 0.330" receiver spacing. Gunsmith's should have a specialty drill bit for drilling the extra mounting hole in these mounts. Anyway, at least my brother had them. With the specialty bit, it really is a simply matter to add the extra base screw hole to any standard 20 moa receiver that may only have the larger spacing for the non-Express Winchester M70 long actions.
Will this work? EGW Winchester Model 70 Picatinny Tactical Rail Mount - $39.99 : Evolution Gun Works , World Class Precision Parts
I bought mine for my Rem 700 from them.
OK, I ordered the nf base today. The tech couldn't tell me if it had the third hole. Thanks