If we are talking to someone who is new to the platform, I would not advise it. A box tune won't SAFELY work for a 3.4 on a gen v without a cam, rockers, intercooler or E-85.
If it were someone who had good tuning experiance with the platform and was willing to take the time to tune and scan, yes it is "possible" to safely run a 3.4 given injectors aren't being maxed, and other supporting mods are in place.
No offense to anyone, but this situation seems to fall in the first category.