Master Brake Cylinder going bad?
 

I have a 1999 Ram 3500 w/ a Cummins and as of lately I noticed that the brakes seem to not want to release when the pedal is lifted, it takes several seconds for the pedal to return "home". I have checked the resevoir thinking that possibly I was low on fluid, fluid is still at top and no leaks/drips that I could see at the rear drums and front calipers. The truck does have 349k on it now. Any ideas?

This is simply a guess, but it sounds like the brake friction material is wore down enough to cause excessive pedal travel.

This would also cause the fluid level to be lower due to the fluid in the calipers "taking up the slack" of the worn pads.

Annnd, if the master cylinder is traveling further due to the lost pads/shoes, it could have went into unknown territory (scaled up or surface rusted portion of the master cylinder bore) which could cause the slow "return home".

Then again, I could be way off the mark.

Sounds like a hydroboost to me, just had the same issue with a 2008 Duramax last week