I have this exact same setup in my 67 Dart with a crane cam I bought back in the '90's. I have another 340 that will be built using the same parts but a different cam. I called comp cams to see what they recommended. They got all the info about my car and they suggested the XE274. Just for kicks ( guess it's just natural for me to ask about the next size up cam ) I asked about the XE275HL. He said that cam would work fine but with stock 340 heads the .525" lift would be more than the heads could handle, so I wouldn't see any real benefit unless I did a little bit of massaging to the heads. So I decided to do the extra work to the heads and have bought the XE275HL kit. Here is a video with a Edelbrock headed 360 with the XE275HL. He is also a member here. His screen name is Sport 360. Here is a link of a before and after picture of his Dart.
http://www.forabodiesonly.com/mopar/...d.php?t=163454
Dart Sport 360 XE275XL Comp Cams Idle - YouTube