Depends if Chuvalo's size advantage would be enough in exchanges. Based on reports, Sharkey was quite quick and Chuvalo was easy to outwork. 50-50 fight, I might pick Sharkey by decision but it's close.
Going with Chuvalo. From what I've read Sharkey was a self taught fighter. I'll go with the schooled stronger man.
This would be some scrap! Both tough, rugged men who came to fight each time out. Sharkey gave Jeffries and Corbett all they could handle, twice each. Believe he had Fitz on the floor before getting KO'd. Chuvalo had some fine wins over top contenders. I believe Sharkey would outmaneuver Chuvalo in a very close but rough battle that went the distance with no knockdowns.
I like Chuvalo. I think boxing had evolved quite a bit and Chuvalo, while certainly a very limited boxer in his day, would probably jab Sharkey's head off. Hard to imagine Sharkey stopping Chuvalo, and without that I don't think he wins against the much bigger, stronger man.
Giving away 20lbs to a super durable guy like Chuvalo, and your not the boxer type. I'll take Chuvalo in a pretty good scrap.