What kind of task is it to modify it to work, anyone done it?

 

Bolt it on, plug it in, hook up throttle cable and air filter, drive it

 

I actually have an L26 throttle body on my Monte. First, if you are still flowing coolant through the TB, you need to oblong the 3 mounting holes to raise it just a little bit to make a proper seal.
I also hogged the thing out to have an exit that better matches the L36 TBody.
Lastly, I ported the inlet. For doing that, I recommend a pre-99 Tbody (as there are two different designs based on MAF type). If you port the inlet, you will need to look at some PCM tuning changes.
I have a full write up, with pics of my current L67 tbody (check the link below):
'04 Monte Carlo SS - L67 Throttle Body

FYI - I hope to sell this in the spring/summer this year. I am planning on an L26 UIM swap and I am working on another L67 Tbody due to some design changes between the L26 and L36 UIM (see how things go later this year).

 

No no, you'll have a vacuum leak, you must create surface area on the backside of the L67 TB for the seal to seal against. Either fill with epoxy putty and sand smooth, or use an L67 throttle body spacer.

Nice writeup Maniac, good pics. The L26 throttle body is electronic, I assume you don't mean it in your posts, actually referring to L67.

 

Thanks.

And yes I do mean mating an L67 tbody to a L26. I can't use the drive by wire L26 tbody on a '04 Monte. ZZP and a couple other vendors sell an adapter plate so you can use an L26 UIM with an L67 throttle body (have the parts in my garage now).