I cut some air filters from a piece of felt, 5-3/8" x 5-1/8" with a hole directly in the center, very easy to duplicate.
I get $35 for NOS filters and $25 for good used ones...plus shipping.
In case you haven't thought about it, the points and condenser are under that cover at the top/front of the flywheel cover. I was able to just clean the points on mine with fine emery paper, paper, and carburetor cleaner and it had spark after having set for more than 10 years. Carburetor is a Tillotson HL, kits are RK88 and should be readily available as they were used on many, many saws.
The 1-70 uses a large felt wick/fuel filter that could well be crusted up from years of setting. You may need to rinse it several times with mixed fuel or straight gasoline to try and revive it.
Mine turned out O.K.
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The Sabre chain was not made by McCulloch. The Sabre brand was very common in the past. They even made some odd pitch chain like this .315.
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Mark