Hi Awesome work:
I am getting on this thread late but hopefully not too late.
I have just started a 2009 6.1L/NAG1 install in a 1967 Polara 500 convertible. Reading your write up is inspiring but also frightening. Nothing ventured, nothing gained!!
Where did you get your drive shaft fabricated?
Also with the NAG1 transmission, the final drive ratio of 0.83:1 means that you need a really low rear end gear ratio around 3.0:1 or lower as previously mentioned. I am looking at a 2.94:1 rear end or even one of the dreaded 2.76:1 rear ends. I am not sure that you can get a sure grip for those rear end gears which means only half the fun...pardon the pun.
Can you get a sure grip installed on a 2.786:1 or a 2.94:1 8 3/4" rear end?
Inspiring work.