After all these years, usually BOTH have been removed. As a matter of fact, the assembly plants were told to remove them and return them to the engine plants as a cost savings measure, but they usually didn't take the time. Once in a while you'll find an engine with them still attached, but it's fairly rare.
Here's a pretty good picture of a 68 L35 with the front bracket, but I don't have any pictures of the rear bracket installed. Note that this is a "mostly" original car, but things like the battery, battery cables, radiator hoses and clamps, belts, the air cleaner lid and filter, etc... have been replaced over the years.
Edit: Good pictures Mike!
Ed