If you havent done this before heres two tips.
Before fitting the points plate and points, sit down with your specs on and find the correct method to adjust the gap, and the timing, study how the eccentrics cannot move anything if the pinch screws are still tight, make sure you fully understand what needs to be loosened to allow the eccentric adjusters to work.
2nd tip, the Idler pinion and AR mech rotate anti clock when viewed from the TS , or in other words opposite to the wheels rotation when travelling forward, this has confused many people, well me at least. This means the points plate moves clockwise to advance timing.
Pages B49, B50 and B51 in the 71 manual
. 3 pages of great info, hard to summarize properly.
In essence set the motor to the timing marks at the Alternator , or use the case timing plug.
Then fit the AR mech loosely , but locked in full advance, adjust points plate so one set of points are just opening. Tap AR mech onto taper,turn motor and set points gaps , recheck timing with fag paper between points , rotate motor and observe strobe marks and fag paper , , coarse tune points by rotating whole plate in slots, fine tune individual sets with the chewy brass eccentric adjuster, when happy tighten up. Do the same for each set. When happy that both sets are opening at the strobe marks, unlock the AR mech and fit the centre bolt.Recheck opening points.
Make a note of which cylinder is on compression for which set of points, make sure the points wires are to the correct coil, swap if needs be.
Some good info herehttp://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=470563