I have a 62 Fairlane with a 302 and C4 transmission, shifted through the floor. Car was originally a 3 spd manual and still has the clutch pedal. I'm wanting better highway manners and would like to replace the C4 with a 5 or 6 speed manual. The TKX is smaller, cheaper, and should require less cutting to the trans tunnel, however, I think I'd really enjoy the 6spd. more. So,,,,,,,,,,,,,,,,
I've got a 302, bored & stroked to 347 and I chose the TKO600 five speed for it. I would have been OK with a TKO500, but at 475 ftlbs of torque output I wanted a bit more cushion. I find that the 5th gear Overdrive is all I need, running 31" tall tires, 4.11 gears and OD 0.64 gets me 1996rpm at 70mph down the highway. With the 4.11's the first 4 gears are amazing, and the tall OD puts me right at the bottom of my torque band on the engine, pretty well flat from 2000-6500rpm.
To me the T56 would be overkill. It's quite a bit bigger, quite a bit heavier, a bunch more expensive and has two overdrive gears, the last one being 0.50 as I recall. It's great for something like the Hemi Challengers, letting them cruise for economy, and drop down to accelerate as needed. With your 302 I'd look at the TKO500. Just my $0.02, your decision.
Wow - looks like Roger is way ahead on this one! Sounds like a TKO500 would be a great fit for your 62.