you can try one more pump to match the one you have. 6 psi is ok with the afbs. but you need to know how much you have when you leave the line. and run a fuel line back to the tank so you will have a return line is the best way to go and is easy on the pump that way you will not dead head the pumps . on the line size i wound run the two pumps in one line the pumps AN 8 to a Y block and to an 10 then AN to the carbs AN 6 or AN8 then run the return AN 8 to the tank and you need a sump in the fuel tank try to keep the pumps at the lowest point and on the the carbs run the off road seats in the carbs : whacked: