The stock engine would be a 216. They should be easy to find cheap because no one wants them. Check the classifieds here or at ChevyTalk.com I believe a 194 is a GMC engine, and may require some engine mount modifications to make it fit.
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'50 Chevy Fleetline DeLuxe ('55 235)
'48 Chevy Fleetmaster coupe ('60 235)
Chicago
http://www.geocities.com/hellfish122