I'm not going crazy on the gear, but I'm going to get a 3000 converter and hope for 11.9s, but hopefully putting in 1.6 rockers will help out the lack of converter/gear.
The .508" cam needs all that gear and converter to run good in a 340. 340's have a short stroke and dont make much torque. If your planning on less gear say 4.10s and only 3000 rpm stall I'd stick with what you have or get something more modern. 1.6 rockers wont make up for running the wrong gear and converter.