Hi Bryan,
TR2/3 and early TR4 use an A-type that's a little stronger shifting than the later TR4/4A/250/early 6.
The reason is a larger accumulator piston. If memory serves, it's 1-3/4" in diameter in the earlier A-type and was reduced to something like 1-3/8" on the later version. This was done... drum roll please... to provide softer engagement! Apparently many Triumph drivers found the rapid and somewhat harsh shift of the earlier A-type a bit disconcerting. The J-type takes it even further and is slower/softer engaging.
Racers really like the earlier version, if they use an overrive. But, one downside is that some of the parts for the earlier version are harder to find.
There are also mods that can be made to all A-type, to make them engage a bit faster. Those mods may not be necessary on the earlier version, but can improve the later one.
Sounds like you've got the early one, which is what would be appropriate to your car.
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