Slant 6 with 200r4?

I know Wilcap can make adapters to mate a /6 with a 200r4. I was just wondering if anybody here has done this exact set up and if so what did the swap cost, what rearend gears are best for this set up, what's the rpms at 75mph, and what is the best mpg you've ever got? I hope to hear a lot of input!:cheers: