Yes, it will stop sooner even if you used the 73-76 A-body discs without power (you might even kiss the steering wheel if not used to them compared to 9" drums). After some hard in town driving you will also you have no real brake fade either compared to the 9" all around.
Measuring drums is the inside diameter where the shoes will cover.
The 9" drum brake spindle is different from the 10" and also the disc brake spindles, so the conversion kit probably uses the specific bearings and races for those spindles which are not interchangeable between each other...on the other hand, there also is the rim issue, 14" rims are necessary on certain upsized brakes (disc especially), so that would also factor in based on the size of the rotor and caliper used (once again going to 10" drums would mean 14" and if you had 13" you would need some new rims...).
It will be better than what you have, but will not be disc brakes. But this will require changing the spindles/possibly upper control arm/ball joint and the lower ball joint.

In a lighter car (say the 1960-1966) the 10" drums wouldn't be too bad if used with a stock to mild engine build. 1967-1972 10" also is a good upgrade but the car is a little heavier. The other advantage to discs over drums is the bias...drum cars tend to pull in one direction when the stop pedal is tromped hard...

2 cents.

-D.Idiot






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Thanks. Sounds like I had better do more looking around and that the kit will not work for me.