I have no direct experience with a sequential, but did quite a bit of research...
The Quaiffe is $12,000 plus the bellhousing is another $1,000 or so. A driveshaft is required as well, but that's not a big deal. The "no lift shift" is an extra cost option. Below is the text from an email I received from the U.S. distributor for Quaiffe regarding this:
I’ve had a couple conversations with Quaife in regards to using a strain gauge shifter with their transmissions and I’ve learned that they discourage it simply because it encourages people to shift without using the clutch which stresses the dogs and decreases the longevity of the dog faces. Additionally, the piezo-electric crystal in a strain gauge does fatigue and will need adjustment throughout the course of it’s usable lifetime.
They prefer a microswitch setup for flatshifting since there is no crystal to fatigue or adjust, the micro switches are either on or off, depending on the location of the shift lever. They mentioned this company’s products specifically:
http://www.geartronics.co.uk/flatshift.htm
Feel free to get in touch if you have additional questions, or if there’s anything further I can do.
Best regards,
Scott Cole
Motovicity Distribution
I have been told that to shift these transmissions, all you have to do is lift ever so lightly off the gas, and it goes into the next gear very easily.
Yes, the EMCO is expensive; $22,000. It's heavy, too. The no-lift shift is another $2-3,000 IIRC.
Hollinger is another option as well.
The guys at Rockland Standard Gear would not sell me a dog ring transmission. They are adamant that these won't last in a Viper.
I have only used T56 and T6060 in my cars, with more longevity in the T6060.