Here's my take, and it's worth EXACTLY what you're paying for it.
Don't do it.
I'm serious, don't.
The 4L80 is in the car, it works, it's handling the power, it lets you cruise peacefully, it saves wear and tear on the knees, any unexpected traffic is a non-issue, and did I mention it's already there?
I think you guys think my knees are made of glass. I can manage shifting a hydraulically actuated clutch.
Re-read the case im making. In alot of instances, over-kill is a good thing. It guarantees piece of mind from breakage, it tolerates extreme abuse, it becomes the equivalent to "bullet-proof"
Except in my case where weight, heat, rotational mass, and friction are all working against the perceived gains because of the extreme duty nature of the beast.
When considering the purchase, I was advised by more than one transmission supplier that " I didnt need a 4l80 at my power level".
This is a fast fckin car, but Here's the three letter problem getting in the way between it being a 7, or an 8 second 1/8th mile et.
L.
A.
G.
Don't get me wrong, I don't intend to try and drag race the car with a CD009 manual trans...But I think the difference of loosening up the rotational drag alone will put this car into its power band significantly sooner than what's happening with the 4l80..
( I really do need to video the acceleration..it goes from me flat footing it and thinking " Any day now" to "Holy sht" in the time it takes to count to three.)
Now, all this could be idle chatter, just as much as the decision to wrap the car like its made out of riveted aluminum. Whether it is or isnt, doesn't really matter because either option could be considered "burning my money". The only difference with the trans, is that I can recoup some of that original investment.
A manual shifted 4l80 with a lockup converter has to be easily worth a grand, that 800.00 adapter, worth 600. That would put a price to convert over to a fairly robust 6 speed at somewhere around 2k after the dust settles...not too much of a stretch all things considered.