Firetruck posted pics of LT and Syncro mirrors and explained the difference. I can't find link to it.

But I do have copy in .doc format 202kb file. Email and I will send it to you.
Link to Wiki pics of Syncro vs LT mirror on T3:
https://club8090.co.uk/wiki/Bo ... ng_mirrors
The "Extra bit" is not only difference. Arm bends above and below mirror are different too. Upper mount packing is different. Lower door mount and packing are different.
To mount LT arms on T3, you will need the upper packing/gasket as it has extra buildup to match T3 door frame.
Lower LT door bracket has 40mm screw spacing vs 51mm for T3 mirror. I was able to get T3 lower mounts, but person could probably fill existing holes in LT mount with liquid metal and re-drill to stock T3 spacing.
I modified LT arms to stand straight on T3 by:
removing the drift pin in bottom of arm/arm mounting bracket,
removing the bracket, (twist, curse, wiggle, curse some more... and finally it will come off)
cutting 61mm from arm,
cleaning arm to fit back into bracket,
drill arm through drift pin holes in bracket, and putting pin back in.

Now arms look straight instead of angling in at top. The vertical part of arm is 60-63mm closer to van then real Syncro mirror arm, but I turned the mirror head so arm grove is inboard instead of outboard of arm. This places mirror in about same place as stock Syncro arm with mirror grove mounted inboard of arm.
As stated above,
email me if you want more info.