Well it's very feasable: here's my LST
http://www.rc-monster.com/forum/showthread.php?t=2739
I'm building a much lighter version right now with hellfire shocks and a single Lipo pack transverse in front of the tranny,motor behind the tranny.
The transverse motor and tranny is the defining feature of the LST IMO(and unique in MTs),weight across the centre line and no torque roll/motor applying side to side force to the chassis upsetting the handling and flight.A transverse motor gives an anti squat effect under acceleration and an anti dive effect underbraking instead,that's why belt drive touring cars (transverse) are so successful in mod class where the handling benefits outway the drivetrain inefficiency disadvantage of belts.(rant over) Also the slipper on the LST is hands down the best in the business,i run a fair bit of slip and it never overheats.
No need for a 2-speed setup really,you're better off with a range of gearing available with brushless,the finedesigns looks to use the std.gearing which will require high rpms to hit over 40 mph,would work OK if it happens to be the speed you want to hit but not very versatile.I'm not a fan of the finedesingns conversions,no fabricated parts for your money,just a pair of BK motor holders,and a clutch bell grafted on to a motor shaft.Personally i wouldn't have the cheek to sell that as a professional conversion but that's just my opinion.I run the FOC on mine,saves alot of weigt and rotating mass.If you buy an LST 2, all else you need is a pair of Nova diff cups ($20) each,or maximizer cups,for a totally bulletproof drivetrain.My transmission has been 100% reliable so far with alot of weight and power.