Re: age from chassis plate
1972 - from 02AK7001 to 05AK2926
1973 - from 05KA5001
1974 - from 08AK6501
Those are AM dates, not calendar dates - so autumn-to-autumn production. But given you're at 07KA...., it's probably that you're out of luck on free tax, somewhere in early/mid 1973 production.
DVLA would need something more concrete - either Citroen Conservatoire can do you an info pack, or Matt Concannon, 2cvgb's reg-of-reg, can get you a club-approved production date which DVLA would accept.
http://www.citroen.co.uk/about-us/histo ... ervatoire/