I don't have a 13, but I used a 9 (from the Super Six donor vehicle) which should give total mechanical of 18. The vacuum pod is stamped "11.0R". I plan to plot the new mechanical and vacuum curves today.
The shape of the curve is as important the degrees in the slot.
The rpm for the advance to begin depends on the spring force of the 'light' spring on its weight.
The long looped 'heavy' spring slows the rate of the advance somewhere later in the curve.
So what advance will look like is not easily predicted.
Take a look through Rick's thread Distributor curve help needed
to see how important it is to remeasure after every internal change.
Everything shown there is applicable to your 6 except the timing curve.
