You said you built the motor? DId you degree the cam properly? did you use the correct balancer and timing marks? You also need to gap your plugs all around .40. The mixture is way way lean and this is not good at all! If its not fixed pronto, you will be re building very soon. Your plugs should never be that white at all. Just make sure when checking your timing you take all the necessary steps because it will determine whether or not you can calibrate your set up correctly or not. as stated earlier 36 total is a good place to start. unless you have a kit to calibrate your distributor then you wont be able to set initial but if you have a gm distributor with stock settings, then where ever 36 total leaves you will work. At least untill you get everything dialed in a lot closer and then you can experiment with a couple degrees or so one way or another. If you bump up your initial you will have to stop your total exceeding the 36.
I hope you can get her figured out before you melt a piston.