Found a crossover pipe for the 3.4 and was wondering if it will bolt up to the 3.0. Figure I could add a blockoff plate and the conversation crossover pipe and be done.

 

The 3.0 crossover fits the 3.0 and the 3.4 crossover fits the 3.4. The crossover you attached here is for the 3.4 but it's for 3.0 swapped vehicles who want to keep the exhaust on the driver side so that it bolts to the rest of the original system. The 3.4 factory exhaust routing is on the passenger side.

 

People also send their 3.4 crossover pipe to Toy Only Swaps and have them cut and re-weld the 3.4 crossover pipe to dump out on the driver side.
I sent mine to them when i first did my 3.4 swap. They did a really nice job.