904/727 dimensions

I notice there are some small diffs between the two. I have a 66 Dart currently w /6 and 3spd manual but will be installing a 392Chrysler with a sb auto. I'm wondering how the installation will go with either trans regarding mounts lining up and so forth. Overall length I think is not a prob since I need a driveshaft anyway made to custom length. Bell diameter difference seems insignificant, bigger hammer. What about the bell to mount lengths? Would the shorter 904 tend to pull the motor rearwards as opposed to a 727? I'll be using a trans adapter, I dunno the thickness offhand, which might compensate a little, maybe.

Car is snow impacted at the moment so i can't crawl under it to see.
http://www.forabodiesonly.com/mopar/showthread.php?t=130450
I haven't found any dimensions for the /6 manual package so I don't have something to compare to. But I need to decide between 727 or 904. Help appreciated.