JonnyBoy

Should probably say "very few interchangeable parts."

It's the same block, but internal parts, heads, intake, etc are different. I will say I picked up 3-4 mpg, more useable torque, and peace of mind after my swap, however if you're doing it for more mpg or power, I agree with some here that it's only worth it if your 3.0 needs head gasket or other semi major work. I was satisfied with my 3.0, and it was my fault(more than the 3.0's) that I blew the head gasket since I overheated it due to a pinhole leak in the radiator. The swap comes with it's own headaches, but it really isn't "just a bored out 3vz."

vasinvictor

iTrader: (3)

Your father sounds ignorant on the subject. The 3.4 is superior in just about every way. See here https://www.yotatech.com/forums/f160/ It's no surprise this is the most common and popular swap for a 3.0 equipped Toyota. I can get 22mpg with 34" tires with 40 more lb/ft of torque. It can be done for free if you play it right- that's buying a complete doner, using what you need, then parting out the rest.

Yodaforce

3.0 was an engineering mistake. I still believe that they used all of the failures of the 3.0 as a lesson and got everything right with the 3.4.
I have passed up $500 trucks in good shape because they had broken 3.0's in them.