Did you block the carb open? Did you squirt some oil in the cylinders first? Your compression readings may simply be the result of stuck rings or rusty valve seats and you may just need to run the engine for a few hours and the compression may come right back. Your engine might have sat with the odd cylinders valves partway open and you have weak springs or gum in there. I would install it and run it for a while and see how it is. Your valve guide seals may be hard and a may smoke but 100+ compression on 3 cylinders will be enough to get it started and then you can re-test it after it warms up.

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