I am redoing a 2nd fl. Bathroom in a 130+ year old house. I am moving the toilet and replacing a shower stall with a jacuzzi tub, the sink is staying where it is. The toilet is going to be appx. 6' from the 3" stack. There are no fixtures above this. I plan on venting the sink and shower together into the stack. Do I need to vent the toilet or am I able to use the stack as my vent? Thanks.

Here is the basic rule; if it has a drain it needs a trap, if it has a trap it needs a vent. I don't understand what you mean with "Do I need to vent the toilet or am I able to use the stack as my vent?" Your old toilet is vented to this stack already isn't it?

The current toilet's drain line runs right to this stack, so yes it is currently vented to the stack (but its location is right next to the stack). I am moving the toilet appx. 6 feet away and am confused on if it needs to be vented differently due to the further distance. Thanks again

No! If all you're doing is extending the existing toilet brain the toilet's already vented. Good luck, Tom