289 vs. 347

Ok i just bought sold my 90 GT and bought my cousins 67 GT. It has a brand new 289 in it with only 500 miles on it. I wanna swap it out with a 347, but i dont know how worth it it would be. For one, i need to know how much i could get for the 289 if i sold it. And two, i want to turn this into a show car rather than a race car, but i also want some power in it. So some advice would be nice here
 
How much are you really going to drive a show car? How much are you really going to drive a show car on California roads?

You probably wouldnt get more than a max of $1000 for the 289 if you can convince someone it really is nearly new. I personally would keep the 289. Its small, but very capable.
 
Have you thought about a turbo charger? Or if you dont want to spend that much how about spending a couple hundred dollars for a nitrous setup. Then you could have that occasional power at the flip of a switch. Easy to install, not much time involved verses an engine change or rebuild and its a cheap investment with a huge gain. Just my 2 cents.