I've got a '54 235 that is running rough and fouling the plugs. I replaced a couple of the plugs with some clean, spare plugs that I had and the engine fouled them as well over the course of about 15 minutes. I had previously set the timing and have made some minor carb adjustments. The engine starts very easily but just isn't running right when a load is put on the motor. I was going to change the plugs with new ones but was thinking that they may just become fouled as well. Any advice and steps to take would be very much approeciated.

1951 Chevrolet 1/2-Ton 5-Window
1938 Chevy Panel