i would not use the 351C, its a great profarmance engine but not really suited for trucks.the 400 is a smog engine which means that it is way down on power.however it can be made into a good truck engine by using a after market timing chain set and setting it straight up or 2-4 degress advanced. all the cams come in retarted mode. offy makes a couple of intakes one is is the dual-port with either square or q-jet.just a polished combustion chambers and exhaust ports.