Here is some info...

Senior Pattern Association - SPA - No planes past 1975, December 31,1975 cutoff.. No Pipes / No Retracts.
No injected engines (YS), max displacement 91 - 4 stroke, electric allowed with a set battery and watt output.
The patterns are made from maneuvers from the era, and flown one maneuver at a time.
To fly except novice you must be a member. Here is the website - http://www.seniorpattern.com/

Classic Pattern Association - CPA- Planes to MID 1990 - Pipes /retracts allowed. Injected engine allowed, max displacement 120 - 4 stroke, electric allowed as by the 1976 rule book. Patterns are flown as printed in the rule book. also flown as pre-turn around. You do not have to be a member to compete. see the mission statement at the CPA website - www.classicpatternassociation.com