How much is this Porsche worth?
 

My mom has a 1976 Porsche 914 2.0L with just over 40,000 miles on it. She's had it in the garage for several years, covered with a tarp, so it's not currently running. I'm sure it just needs some minor tune-ups, like battery charging and such, to get it going again. Other than that is in in very good condition ATEQ VT55 OBDII TPMS
.
She is wanting to sell it, but does not want to under sell it. I've looked up average prices for similar models, but I'm sure they are in running condition. Any idea how much it would be worth?