Changing to a 700 r4 will require you to change both driveline lengths and move your crossmember. As far as loosing rpms and some power I would say yes you'll loose some since a 700 has a 1st gear ratio of 3.06 and a 350 has a 2.52 ratio first and i'm thinking 2nd is about 1.63 in both so I think you can see the difference. But if you have enough ponies under the hood you should be ok. I would say a stock one should handle your horsepower numbers but anything higher than that it should be beefed up a little.
