I have a t5 v6 tranny,can I use that shifter in my v8 t5 tranny?and when I do the 350 swap and and put the v8 t5 in will I beable to use the stock 6 cyl t5 crossmember on the 8cyl t5?

Sure you can use that; if you like your shifter to swing around the car so far that it hits the passenger and the radio and maybe the dome light, like it does now; and feels like there's a bowl of oatmeal serving as part of the linkage somewhere, like it does now.

If you're upgrading the engine, upgrade the shifter too. You won't BELIEVE how much better practically anything is that the crappy stock thing.