Parallel fuel rail kit
 

Where's the best place I can get a parallel fuel rail kit for my version 2 gc8?

IMO most places either over charge for these, or they are ebay kits using cheap parts. You obviously want a bit of quality when talking about high pressure fuel.

If you are handy with these sort of things it's not too hard to make the kit up yourself. You will need a couple of fuel rails (either new ali ones or chop up and modifiy stock ones), two t piece joiners, four or more 90 degree elbows (depending on how you run it), an fpr, a gauge and some good hose and clamps.

Tips:

Be careful which connectors you get. Most people use ali 6an connectors which are ideal but there are a lot of different style all of which hold the hose in different ways. Some are better then others. There is an ebay company called torques which are recommended and supply good stuff at good prices.

Make sure the FPR is AFTER the injectors on the return line.

Make sure if using braided hose that the hose doesn't touch anything else. It acts a a file and will cut through rubber hoses or wires, ever metal work due to engine vibrations.

Use a gauge to make sure that you keep stock pressure.

When fitting new rails use new injector o rings and rail seals as a leaky injector can kill the engine or a leaky rail can set fire to an engine.

Don't have the hose bend too much as it puts pressure on the fittings and the hose walls. If it has a tight bend use another joiner of the right angle.

Try cdf racing mate

I got my kit from CDF, most other required parts from Lateral Performance.

Alyn AS Performance or CDF

One tip is to use the same manufacturer for the hose and fittings, as been stated can vary slightly from one to another. I have rcm rails and a fuel lab fpr, all hose and fittings supplied by torques