83 will not start

put a new holley carb and edlebrock intake from summit on my 302. cannot get truck to start. have firing order 1-5-4-2-6-3-7-8, have set timing 10 degrees BTDC, if i retard carb backfires and catches fire or fire blows back thru carb. If i advance it will not fire. any suggestions?
thanks in advance