It appears that ZF Transmissions has the four wheel aftermarket crowd in mind.
Per the ZF web site: "The new generation ZF-Ecolite "Universal" can be adapted to the individual conceptions and requirements of manufacturers. This modular design offers the possibility of adapting a flexible, tried-and-tested gear unit to customer-specific engines (specific or standard clutch bell housing) and different shift control variants. Advantage of the universal series: Also small series can be produced at satisfactory cost levels"
ZF six-speed manual transmissions. The universal model "6 S 381 VO" and possibly the "6 S 351 VD") seem well suited in terms of size and weight. The "6 S 381 VO" has a 0.08 6th gear and a 5.40 1st gear while the "6 S 351 VD" has a 1.00 6th gear and a 6.70 1st gear.
Installation length: 658mm / 25.9055" Weight: 63kg / 138.891 Lbs
formatting link
Someone, please make an adapter kit.