Have a look through this thread. http://www.ten-tenths.com/forum/showthread.php?t=81326
Then you might see what the variety was between Group 1 and Group A versions. From there I suspect you'll find a few posters who can assist.
Also I can direct you to Ken Clarke who operates out of Hinckley in Leicestershire. His phone number is +441455 615768. He worked on the competition cars in the TWR days.
Are you building it for the track and if so, where will you race it?