There were several different parts used throughout the TR4 production. A few years ago I ran across the engineering drawing for the two normally used on North American imports.
As shown in the picture, the one with the three button plugs on the car with the gray carpeting is the earlier version.
The one on the car with he radio is the later version and has a larger cutout for a radio
The dimensions and angles between the two are also different. Example, indent after the first bend from the bottom mounting part on the older one goes in deeper then it would go out on the newer bracket that faces outward.
My 1962 Bendix R2BT4 radio will not fit into the older style bracket unless the bracket is in like your gray carpeted car photo.
I believe the change took place at body number 8380 CT. There were also several different bolts used to mount the bracket just above the heater controls. I have seen original photo of hex bolts, pan head phillips bolts and counter sunk phillips bolts with finishing washers. There is a photo near the back of the original TR4 repair manual showing a car with the counter sunk phillips bolts and finishing washers as used on my car. I have had to use that photo to prove originality at car shows.