Question on Technology Changes in Race Cars  

A fellow who visits the Vault who also builds 1/25th size asphalt modified models emailed me the following two questions that I'm hoping you guys in the know can help out with, and maybe give a few examples:

1. Around what year(s) was the switch (asphalt mods) from drums to disks?
2. Around what year/years did the asphalt run big blocks with injectors?