There is nothing wrong with running the 33/22 combo you have. It will slightly change the IR of the car, but probably not noticeably.
The 56T total was very important when running the plastic/alloy gears, however with two steel gears, you can get away with running 33/22 as the gears will not break.
The IR with 23/33 is 2.58
The IR with 22/33 is 2.70
This equates to about 0.5 on an overall ratio, which roughly means going up 1 pinion.
The 78 Spur doesn't appear in the manual because it's not a Schumacher product, I believe RW Racing make it.
For a SP V3.0 6.5 I would run an overall ratio of ~8.50
You can get this using your current internal gears (22/33) and your 78 spur by using a 25T (8.42) or 24T (8.77).
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Yokomo - LMR
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