Inline 6 drive train advice

[62 bigwindow]

I have come to the point on my 66 that I am ready to install motor and trans
to mock up ride height for the bag mounts on the rearend and have decided in order to be a little different go with a mild 250 inline 6. My question to you guys is what trans to go with and what rear end gearing? I plan to run the stock 12 bolt rear end. I was thinking of the 700r for the overdrive and ability to cruise at highway speeds. As always thanks in advance for any and all input..