Jay, not sure where you heard that a Lenco absorbs more power than an automatic, but I doubt it. Several guys in our local stickshift race group, use Lencos,and I asked one of them about that, and he says they do take some power in low gear, but after every shift, you reduce that drag, as you are not running thru that planetary gearset any more, and by the time you are in high, its close to the same as a regular stick trans. Many of you guys might be familiar with this fellows "slow" street car, and blue 67 Fairlane, that runs mid 8s with a naturally aspirated small block Ford, with a 5 speed Lenco ST1200 "street" transmission. Google his name, Grant Klohn, or check on Youtube, there is a number of videos of his Fairlane out there.
On a personal level, I can give 2 examples on my own cars. My 428 FE powered Fairmont ran a best of 10.55ET @ 126 MPH with a pretty good C6, low drag Torrington bearings thru out, reverse pattern, transbrake valve body, and 8 " torque convertor. With the C6, I could go 4500 RPM with the brake pedal, and normally launched at WOT with the transbrake, which allowed 5200 RPM. With NO other changes, than replacing the automatic with a Jerico 4 speed and McLeod "Soft Lok" clutch, the car improved by over 1/2 second and 6 MPH (10.03 @ 132MPH). If you want a more street friendly application, I used to have a different 78 Fairmont, daily driver that saw weekend strip action. It had a mild 302, and with a C4 with a shift kit and 2600 B&M convertor,and 3.55 gears, ran a best of 13.72 @ 98 MPH on 8 1/2x26" slicks. I later changed from the C4 to a stock, Junkyard T5 from a 5.0 Mustang, with a Hurst shifter and a $169.00 stock replacement clutch kit. Again, I changed nothing else on the car, and at the track, it improved by almost 9 tenths and 8 MPH, best of 12.80 @106 MPH, on the same slicks. On the occasional "Street Legals" race, I ran it on the Grandpa 205/75R15 whitewalls, and it would still run 13.30s, leaving just above idle, which was almost 1/2 second quicker than it ran with the C4 on slicks. Also, compared to the C4, the T5s overdriven 5th knocked almost 1000 RPM off the freeway speeds, and obviously that was a boost for gas mileage. Of course, some guys can run slower with a MANual transmission, I have seen them do just that, but after watching their feeble attempts of driving with a clutch, I have determined they couldn`t drive a thirsty duck to a water filled lake!
By the way,the quickest car that I have driven to date, was a tube chassis, Super Gas 86 Thunderbird, with a 460 based Ford big block, and air shifted Powerglide. Along with being the quickest I have gone (9.3s @ 138 MPH), it was hands down the more boring car I have ever taken down the 1/4 mile. To me, if it ain`t fun, I don`t wanna drive it!