In my case, as far as I wanted!
They are actually not stock. I found them in Napa for about $7 a piece. They came in about 6 foot sections, and are very easy to cut. I just put them where I wanted them, then ran the wires. Once I had it dressed in where I wanted it, I pulled about 5 inches of wire out (pulled the knob out 5 inches) and cut it there. Then, pushed the knob back in, and hooked it all up.
I couldn't tell you how far you could get away with the stock ones though. Sorry. But, for the price, you can't beat just going the napa way.. and hey, you didn't even notice they weren't stock, so who would! ;D
I'm not sure which dash light bars you are talking about... ? I got all new ones with the wiring harness for the gauge cluster. They looked like generic, simple light bulbs to me. I imagine you can buy them at a parts store without any problems!