Todd,
Check the firing order of your cam. A 351 has a different firing order than a 302,but if you have a 302 cam in your engine you can just change the spark plug leads to that firing order and it will work.To check, pull the valve covers off and and rotate engine over slowly,when the intake valve is closing ,that cylinder will fire in about 90 degrees. Just check in what sequence the intake valve closes on all 8 cylinders and write down that sequence over 2 engine revolutions.Check the plug wires on the distributor to make sure they go to the cylinders in that order.It is a common practise to put a 302 cam in a 351 as it's cheeper and there are many more cams to select from.
hopefully this will get you going.
Perry.
