wont spin

I also agree with Demonseed, 800 cfm for your combination is too much carb. Your cam is just a step up from stock. A higher stall converter and a smaller carb (around 650) would be an excellent match for your 355 gears. You didn`t mention your ignition, but I would make sure you`re running a quality ignition with the timing set properly, perhaps 34* total (initial and mechanical, no vacuum included). If you want to drive the car on the street and you value your gas mileage then keep your vacuum advance. If your only concern is performance then plug your vacuum advance and get your mechanical advance set up to completely come in by 2400 rpm. Is this a 68-71 340?