Will the lmm bellhousing bolt right up to this built 05 trans I have?
Sorry read it wrong. Are you asking if a 6 speed bellhousing will bolt to a 5 speed trans case? Or are you asking if a 5 speed trans will bolt to an LMM engine?
The 05 bellhousing will work in the 08 just fine. 07.5+ don't have the speed sensor in the bellhousing, so an earlier one will work in a later, but a later won't work in an earlier. And it sounds like you already know you'll have to swap shift shaft, valve body, and ims in to make it work.