The OP needs to read up on bike fit and at least take an accurate cycling inseam measurement from the floor to saddle-like crotch contact in bare feet. From there, a reasonably accurate saddle height can be deduced and then an appropriate head tube length.

The idea that TT length is more important than any other dimension is wrong. TT length, by itself means nothing. A seat tube angle is also needed to determine the frame reach. The head tube length changes about twice as much as the reach, between any two frames sizes, so you can't ignore the head tube length and only look at the reach.

The OP is so tall that only the very largest size that most brands sell would be suitable, particularly if his inseam is 36 inches or greater. The fit calculator below will get you started, but I would not put much value in the output. At least it tells you how to measure inseam.

http://www.competitivecyclist.com/za...LCULATOR_INTRO