While the front mounted 50 cal was not a standardized or approved modification, it was done with fair frequency. As such, there is no right or wrong mount to use. Some of the photos I have seen show them using the same mounting bracket as the halftrack. BMGParts has them listed on their mounts page.
http://www.bmgparts.com/mount.html
Then you would just use the standard cradle.
I can't help think that the 50 must have really rattled the armour on a carrier.
For the smoke discharger mount, I believe Rod Shaver has them, either originals or repros.