Calculating Tesla coil Primary
of course you don't want to to remake the secundary coil.

I've made a tesla coil my self three actually before one worked.

What you need is "THE SPREADSHEET"

you can download that file at the bottom of this site: http://home.wtal.de/herbs_teslapage/design.html

then fill everything in what you know and what you have
and then just play around with some values of the things you want to change to make it all come out accordingly to your secondary.

Then you can proceed to the most important step where "the magic comes".

Tuning:

-you've to get the primary's oscillation frequency the same as the secondary's resonance frequency
-you can achieve this by searching for an ideal point on your primary
For this you'l need an oscilloscope and a waveform-generator
more information about tuning here: http://www.hvtesla.com/tuning.html

good luck with building your coil!