Where can I acquire very precise sun centered planetary orbital data?

I would just use the JPL ephemeris, and subtract the position of the sun from the position of each planet. That will have exactly the same effect as fixing the sun's position at (0, 0, 0). The JPL computers use 63-bit (18 decimal digits) precision, and sophisticated equations of General Relativity (GR).

The orbit of Mercury is determined to an accuracy of a few kilometers. There hadn't been a high-accuracy radar measurement of Mercury's orbit since 1999, until this year's MESSENGER spacecraft. The data from that hasn't all come it yet, and will take a while to crunch in the computers.

I don't understand why you say "Newtonian level equations". You need to include GR effects to get high accuracy. As for the sun's mass distribution, the J2 zonal harmonic is enough. There have been studies that include J4 and J6, but these are for studies of the sun's interior, not the planetary orbits.

Note: VSOP87 is outdated (25 years old). EPM2008 and DE421 are the modern standards.

Try the JPL ephemeris. I don't know if there is a sun-centered ephemeris that the general public can access, but here 's a link to the Google webpages that includes down-loadable software sites:

http://www.google.com/search?sourceid=navclient&aq...

I always use Mathmatica for my celestial modeling and is is very easy to transfer the equations from Mathmatica to your program

vsop87