I don't have bellhousing to tailhousing measurments for a 400 and 465 in my head, but if your no worse off than a TH400 with the 1.1" adaptor, then I wouldn't worry.
My wheelbase is 112", but I think with the 52, and 63" spring swap, each end has been stretched fairly evenly. Currently I have driveshafts of exactly the same length, which defanitly has its merits.