Recommend a cam and converter for 340

I think any of the modern cams would do well. I like both the XE268 and the Voo Doo (Lunati lines but my preference for you would be the XE268. It requires less spring which means the heads dont have to come off where Lunati calls for dual springs. The Lunati is a little more aggerssive IMO and if you were having the heads done too, I'd go with the 60403 and run the dual springs.
For a convertor... I've had good luck with the Mancini Racing 22-2500 stall convertors. Cheap, and decent. Not a race unit but for a cruiser with a mild engine they would be fine. If you want a real deal, talk to Lenny and Ultimate.