Hmmmm..... The asking, $58,900, seems a bit over the top and I do not see this car as a market setter. The USA Carrera is a desirable car (especially 1974) but tend to have askings from the mid 30s to mid 40s.
This one has been on EBay forever @ $46,500 asking
http://cgi.ebay.com/ebaymotors/1974-Porsche-911-Carerra-Coupe-/300440616405?pt=US_Cars_Trucks&hash=item45f3a7fdd5 #ht_3424wt_1167
This one is at Sloan and they want $65,000+
http://sloancars.com/1689/1974-porsche-911-carrera-sunroof-coupe-bahama-blueblack-45000-miles/
The euro carreras of this vintage certainly sell in this price region and much higher due to the 911/83 MFI motor. These cars start in the high $70s.
This 1975 Euro they are asking $80,000+
http://www.porscheplanet.net/Classifieds/1974%20911%20Carrera%20Euro/1974%20911%20Carrera%20Euro%20Info.htm
This 1976 Euro they are asking $175,000
http://atspeedmotorsports.com/76_RS_Media