Need help to decide what rack and pinion to use in a 6'x10' table

Hello,
Im confused on which combination of rack and pinion to use for a
6'x10' table.
I know that there are three steps to solve.
1.- which presure angle (PA) to choose, 14.5 PA or 20 PA? I know the
20 PA will hold more load than 14.5 PA, but how much is more? does
this size of table really benefits using 20 PA? what is the
important facts to know to make this decision?
2.- after knowing what pressure angle will be used, the next step is
to decide the diametral pitch to use. So what is necesarry to
consider in this decision?
3.- In this step we already know the PA and DP we are going to use,
now comes to decide how many teeth on the pinion, so what governs
this decision?
Is hard to find some 20 PA conbinations i been suggested earlier. So
if this questions are really hard to explain, i'll be happy to have
some suggestions without explanation and where to buy them online. I
think is better if someone could really make clear this for me and
others, i guess other have the same doubts.
Kindest Regards,
Hector Quintanilla