Sooty, black plugs ???????

[lotsagas4u]

Have a 36 LB engine that's easy to start first thing{warm weather}, drive it awhile, 10 miles or so, its harder to start. I have tried several plug variants, ngk ab-6, autolite 386, gap 0.25, it fouls them all. Have a newly rebuilt, max 97, charlie tested, fuel pump, and a skip haney coil/set distributor. Engine runs well, drive it 45 to 55 mph tops. It runs around 190 all the time. I use no corn gas, and yes its fresh, any thoughts here? Thank you