Hello,
I purchased the tach in the picture. It doesn't come with a Shelby GT-350 bracket to mount to the dash.
Looks like you purchased an over the counter 66 style tach. Looks pretty aged so likely not a repo but you can check the back side of the tach workings for a date stamp
Question 1: What is the difference between a sun style tach and a original factory made 66 Shelby Dash tach?
Allot - Suns of that period required a light second box normally mounted in the engine compartment. Both were made by different companies.
Question 2: Is this the correct bracket I need for the tachometer have?
You didn't post a picture of a mounting bracket Believe there were two brackets available one for steering wheel mounting and one for dash (66 Shelby style) mounting
The use of the search feature using the words "66 tach" turned up the following
http://www.concoursmustang.com/forum/index.php?topic=11174.msg66830#msg66830And another this set of instructions that would have come with one of the kits