I would like to add the fact that the ZF 6 speed is a double overdrive trans. 4th is direct drive, 5th is .7:1 and 6th is .5:1 . That means the drive shaft is turning twice the engine rpms, when in 6th. The Vette shaft is short, aluminum and designed to spin that fast.
I also have a 4+3, in a '87 coupe.
You said, "I own one and like some the way it works (most the time)".
I know exactly what you mean. Sometimes the computer doesn't think the way we do and you have to remind it, what it is you wanted.
A lot of people have removed the 4+3 in favor of a 5spd or 6spd. Sometimes it was because the OD unit broke, but I really think most of the reasons were because of electrical problems or the driver never learned how to use the trans.
I've also noticed that the guys that replaced a 4+3 for a 6spd ended up also replacing the rear gears. The 4+3 used 3.08 and the ZF's used 3.43 rear gears.
A couple of years back, Tony posted some pictures here of his Saginaw 4spd mated to a OD(from a 3spd). That's as close to a 4+3 in a truck as I have ever seen. Just no computer.
