Will Rod swap require balancing?

It depends on what year 318 you have. Newer 318's used the same rod forging as 340's and 360's. You can compare rod forging numbers. Past that It is worth the money to have your engine balanced, since it runs smoother and will last longer. You do not need a fancy fixture, I used a home made tool to balance rods, I'll try to take pictures next week. The ends need to be parallel, and as a check the ends should add up to the total weight of the rod.