Well I have the 1938 Elmar up an running on the M8.
What you need:
An old style Leica LTM to M-mount or a Cameraquest Type I.
A Leica SOOGZ.
A 39mm IR Cut filter (I used a B+W to save a few bucks)
A Heavystar Leica 35mm 39mm vented screw in hood.
I went with the SOOGZ because it allow me to quickly remove the whole unit and set the f stop. I can also us it with a 35/3.5 Summuron.
I've posted some quick shots with it on my Gallery.