Looks like a clean California car here - would be a lot of fun to swap in a big-inch mill and maintain the low-key look.
Interesting that a '71 model car would have CA black plates. Might have been plated in a small town where they took longer to deplete their plate inventory (typically '69 would have been the last year for black plates).
Have to ask...what is the purpose of that huge horizontal gash in the firewall above the master cylinder?
Link to 1971 Duster auction
VL29C1E116469