Is it possible to use 6GB of memory in my MacBook Pro 3,1?
Yes. I own a MacBook Pro 3,1. I installed 6GB memory and have been using it like that for more than two years. Note the specifications below. You can call the tech support people at Other World Computing if you have any questions.

The RAM in my system is as follows:


Bank 0: 2GB DDR2 SDRAM 667 MHz
Bank 1: 4GB DDR2 SDRAM 667 MHz