Pre 71 servo or o-ring cap

So like the title says I’m looking at two ways to go. The 727 is being rebuilt at the moment so now would be best time to improve while it’s open and there. Little 318 non racing but looking for best engagement.

Either :
1 I have a complete pre 71 (I believe) maybe 70 early servo.

2 or the larger one that came out of the trans (1974) with the Sonnax O-ring piston cover cap.

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