M1 or Port-Matched LD4B on 408

my 360 starts well with a 750 avs and no choke at 30 degrees air temp. not jetted super rich, ld 340 with center divider cut down 1/2" and blocked exhaust crossover. 4 gear manual and 4.30 gear and 28" rear tire. will not idle for about 10 minutes, but I can drive off in about 2 minutes after fire up and go as slow as about 10 mph