I am using the 3/4" forward mounts and only have about 1/2" of clearance at the back of the cap. I do not think my distributor will come in and out with the cap in place. I am planing on using a long water pump and a recored 6cyl radiator in the 6cyl position. I am not using headers. I am using late model truck ramshorn manifolds. You might want to check with Mike McCulleys Classic Chevrolet 559-226-8196.