Yes, what the others have said. Just figure out where you want the bracket to end up, then either decide whether the floor needs to come up to meet the rear bracket, or vice-versa. You'll probably end up needing to make a spacer to fill the difference. I had a similar situation mounting the Miata seats in my car, but I kept the tilt-forward function and didn't attach them at the rear, just have adjustable legs coming down to the floor.
 

Thank you both for your input, I really appreciate it.  
I know I have a bunch of work ahead of me with this project and bought these Corbeau seats because they have brackets for the Mini and I thought it would be one less thing I would have to worry about fabricating.

I looked at my old seat, yes it does have a U shaped bow at the rear, and just sat down in the back. Interesting design, I work at BMW and never have seen anything like that .
I will try your method and try to bend it.  I was a little scared of drilling through the floor underbody but if that is what is required. I will look into doing that.  
Would you have any pictures of your setup?

thanks again

YES you have to drill the holes for the seat bracket, in the original seat fit these were not bolted down to allow the seat to tilt so you could actually use the rear seat...........

From the pictures and what you have said i assume you are referring to the rear brackets and the space between the floor and the bracket.
A few things come to mind.

Is the original seat lock U shaped bracket that is still in place holding up the new frame ?

If you trim the carpet around the bracket where it lies on top of the cross member you effectively move the bracket closer to the floor, they may have been fabbed up originally on a Mini with no carpet.

The new bracket is made with a 90 degree turn on top of the cross member but it may or may not be a full 90 degrees. Put the bracket in a vice where the bend is and push down on the rear of the bracket not aggressively just enough to tweak it that will get the mounts closer to the floor.

Or just mark the spots where you need to drill the rear holes and put the nut and bolt through and just pull it down.

Like Paul said they are never 100% and as with most parts produced offshore now they all require an extra bit of effort to fit correctly.

thank you for your help

but if you look at the back of the bracket, there is no hole in the car for the bracket to bolt to.  
Do I just make my own?  It just doesn't seem complete 

Are youtalking about where the rear legs bolt down? If so they never do just touch the floor. The mini floor is very flexible and bends all over the place. Either bend the floor up to the bracket or use a spacer

https://drive.google.com/drive/folders/0BxqQBb5LlQNCTXhVUG1BVFRZXzQ?usp=sharing


those are all the pictures I took, I can try to take some others. The concern is at the back where you can clearly see the gap between the floor and the bracket.
Basically Corbeau U.S. told me I am out of luck and sorry .  There is no Canadian Corbeau so I guess I will have to try the U.K. when I can.

Well the photo doesn't help much at all. Perhaps more light and a full picture of the problem area?  I've fitted lots of corbeau brackets without problem sometimes they need a small tweak but not more than that. Oh and spend the extra and call corbeau in the U.K. They are most helpful 

Hello all,

I am trying to restore a 1994 Mini I purchased and turning into a vtec Mini.  I have the motor and bits but still need the subframe.

Regardless, to minimize interior fabrication, I purchased a set of Corbeau seat brackets that are made for the 66-00 Mini body.
Has anyone tried these before?  
If you look at my picture you can see that the back does not line up at all.  
I tried to contact Corbeau and they are giving me the total runaround.  I am so upset and just want a solution from them, they keep telling me it is a problem with my car and not their product.  If anyone can assist, I would be ever so grateful.

Thank you,
https://drive.google.com/open?id=1bymJvejPksC2z0I1HJuD98bhBk3wa3lSVw

https://drive.google.com/file/d/1zE_WyuW51v36o-respITGzFt9xteiVVKQA/view?usp=sharing