Havin a numbers matching car is always better for resale as an original classic.
A car can only be original once... after that it's what the market will bare or if your lucky finding that special buyer willing to pay what it's worth to you.
Is it rare? Well numbers wise:
According to NastyZ28. http://www.nastyz28.com/camaro/camaro79.php
In 1979 there were 260,658 V8 cars and 84,877 were Z28's The rest Base, Berlinetta's or Rally sports could have added the RPO LM1 350 factory option listed as $360.
According to Old ride -- http://www.oldride.com/library/1979_...et_camaro.html
1979 Base Camaro 111,357
1979 Berlinetta Camaro 67,236
1979 RS Camaro 19,101
1979 Z-28 Camaro 84,877
Hagerty lists the 1979 Berlinetta 350 option car about $2,500 more than a Berlinetta with the standard 305 witch is not bad for a $360 option!