hokay,here's my best guess,the two 56a boxes are a12 4 speeds,one first with ribs is 1200,the second with no ribs is either 120y or sunny.the second 'reversing light'switch is a top gear switch for emissions.this turned off the vaccum advance to the distributor in any gear but 4th,note the different spade connections so you can't get them mixed up with the reversing light switch.the third box is just a 4 speed that is worn in the shift mechanisms,this allows the shifting rods to go into a position where there isn't really a gear.have been caught once or twice myself in wreckers with this one,but a quick check of the actual box put me right.the gearbox is still alright to use,just don't try to flat change into 5th.the way to tell an a14 gearbox from an a12 is the distance between the bellhousing( the part that bolts to the engine) & the front bulkhead of the gearbox (the part the throw out bearing housing bolts to).this is longer on the a14 boxes,4 or 5 speed,resulting in a clutch fork with a right angle at the end.if the clutch fork is there,this is another quick way of checking what type of gearbox you have.yet another way to check is to just pick the thing up.the a14s are heavier enough that you notice the difference in effort.i've been told the best gearbox to use of the two a12 boxes is the 1200,as it has a stronger bearing were the cluster gear sits in the front bulkhead,not a needle roller like in the 120y or sunny(b310).i've been told these early boxes will take 200 hp,though i've never seen this myself.