The radiators are the same part number, so there is no difference in the "piping" or cores between the V6 and V8. Many on these forums have performed the bypass, including myself for a short period of time. While I replaced the radiators and chose to utilize the radiator's integral trans cooler, that was my preference. There are many here that have done just the bypass and use nothing but the auxiliary trans cooler, even some who tow, and have not had any issues. As I mentioned earlier, you do lose some cooling capacity and the warming ability, but I've yet to hear of anyone who has experienced any problems while running the bypass. Those that have monitored the trans fluid temperature while running the bypass have actually stated temperatures on the cooler side, between 150-165 degrees F. Ideal temperature is around 175-200 degrees. You might find this temp chart useful:
My advice is that if you have any doubt or concern, just replace the radiator and give yourself piece of mind!