I just made the swap from a T350 to a 700r4, which you can see in my build thread.
I had to shorten my drive shaft about 3", move the crossmember back, run trans lines and a trans cooler and use a flexplate. You'll have a very nice 1st gear and more importantly to me an overdrive.
The cost of my trans which is GM rebuilt from a 91 Corvette was about $1500.
Hope that helps.
