Why am I so slow

The carb is fine for the motor. 340s like big carbs. Mine has a 830cfm Proform on it wich is the same thing Joe has on his 360 in his Dart.

You need more converter. that cam is 248* @.050" You need 3000rpm stall if not more.

I also doudt your compression is over 12:1. You'd need a pretty big dome or real small chambers to get that short stroke to make that much compression. A big dome wont ft under the edelbrock heads with out a lot or machine work. Your probably closer to 10.5:1

Whats your timing set up at ? I would start at 16*-18* intial and 34* to 36* total all in by 2500rpms.