2.02 heads on a 318

The chambers in the 340/360 head are larger than the chambers in a 318 head. So when you put a 340/360 head with 2.02 valves on a 318 you loose compression and low end power. Also the 340/360 head has bigger ports so when used on a 318 the intake velocity is lower which also impacts low end power.

The easiest, most straight forward and least expensive thing to do is build a 360 vs stroking a 318. Even if you already have the 318 and need to purchase a 360 block it will still be less expensive.