Big Valve X Heads on Low Comp 72 340

What cam are you running?
Honestly, you'll probably be able to tell zero difference with your setup. If you put 2.02s in your existing heads instead of the stock 1.88s, there would functionally be no difference in the heads at all.
Aside from the resto crowd, the only advantage of X heads over, let's say J heads, 308s, or 576s is possibly the amount of meat available for porting, the port sizes and general profiles remain basically the same;
so in a mild build like yours you'd likely not notice any seat-of-the pants difference, as I doubt your cam can really take any meaningful advantage of the 2.02 valves over your current 1.88s.
If you plan on further building your motor, save the X heads for that time.