[totaltec]

Hi Jon. I looked into this for you and found that the template that controls this JS is: **YOUR-SKIN-DIR**/modules/Product_Options/func.js

Around line 187 find this:
/* Update price */
if (document.getElementById('product_price'))
document.getElementById('product_price').innerHTML = price;

And change it to:
/* Update price */
if (document.getElementById('product_price'))
if (price == '0'){
price = "Call";
document.getElementById('product_price').innerHTML = price;
} else {
document.getElementById('product_price').innerHTML = price_format(Math.max(price, 0));
}

Now this isn't going to handle everything for you, this is just an example of where to get started, and how to go about making the change that you want. There may be other ways, this was the first solution I came across.