The early Rochester 2GC carburetor that was found on 265 and 283 Chevies of the '50s and '60s will bolt right onto your manifold, and a lot of flathead guys with the Merc 4-bolt manifold have taken advantage of that fact and really love the way they run, and their simplicity. They can still be found at swap meets and on eBay. Rebuild kits are available. See the link below! DD
http://www.carbkitsource.com/carbs/t...Jet-index.html