Will a 340 intake fit a 273?

Check here...

http://www.allpar.com/mopar/4bbl.html

Hopefully this will help. The early 1964-1966 273 heads were drilled at a different angles and will not work. The head bolt pattern is the same for all small block, pre magnum heads, X heads w/ 2.02 valves will hit the 273 block because the bore size is too small. The 273 heads are closed chamber and you will loose quite a bit of compression moving to J heads, open chamber, from a 318. The early 273 engines are not any fun to try to hot rod and unless you are looking to keep numbers matching you can build a great 318 engine and the only thing that is really different is the LEFT engine mount, it is reversed. Easy to overcome but be ready to scratch your head when you drop the new engine in. You will need a saw, a washer and a welder to convert the motor mount bracket. 273 exhaust manifolds will not fit on anything but 273 heads, they bolt up and look good and then they leak. I've built every small block 273-340 combination you can dream of. All the best. NSF Racing