I just installed yet another set of front seat belts.

[Stanglover]

Stanglover what brand did you install? I don't see an option for the Long C bracket on any site I've be to.

Wesco. (aka Seatbelt Solutions)
You'll need to search for 71-73 Mustang.
Here is a link to the Mustang belts. The kit shown includes the long C bracket, but I would suggest contacting them to make sure. Also contact them to order the drop sash.
However, as I said, the center tunnel belt does NOT fit very well. When I had this in my car, I removed the plastic cover and bought "sleeves" from Seatbelt Planet separately. Regardless, these center belts are about 2" shorter than the original Ford center belt. Not a problem for taller people, but puts the buckle to the side and behind a shorter person.

https://www.seatbeltsolutions.com/mustang

 

[TheDude]

Not sure if this is relevant here, but I recently ran into another local '72 owner that installed a simple drop for the shoulder harness and just installed one myself. Basically just using a bolt in seatbelt extender connected up at the roof and then screw this to the top connector on the shoulder harness to lower drop that down to whatever height you want.

Haven't driven it much yet, but looks promising and is definitely more comfortable, cheap and super easy to install in a few minutes. It's all rated for seatbelts so should be safe as anything else and looks pretty stock.

 

[Stanglover]

Not sure if this is relevant here, but I recently ran into another local '72 owner that installed a simple drop for the shoulder harness and just installed one myself. Basically just using a bolt in seatbelt extender connected up at the roof and then screw this to the top connector on the shoulder harness to lower drop that down to whatever height you want.

Haven't driven it much yet, but looks promising and is definitely more comfortable, cheap and super easy to install in a few minutes. It's all rated for seatbelts so should be safe as anything else and looks pretty stock.

View attachment 87452

If it works and doesn't compromise safety, why not.