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They should help significantly, in general there is no downside to larger valves until you run out of room in the bore. And that advantage is at lower lifts, which means that they help power even with a stock or mild cam. You don't need a big cam to take advantage of the greater flow.
You will need to have hardened seats put into the head on the exhaust side, so be sure to budget for that too.
If you can have the machine shop run a 'bowl hawg' (75 degree cutter) into the port after cutting the bigger seats that will help significantly too.