5 point harness in a car w/o roll cage...How to do it?

Alright, I am converting my duster from a column shift bench seat to a bucket seat floor shift. I am not using a pair of factory seats, I am actually using a set of aftermarket seats that allow for the shoulder straps of a 5 point harness. Since I am not going to be putting a roll cage in my car I was wondering what the best way to tie them in to the car would be? I have thought about making a big beefy set of brackets that are welded to the sub frame connector but I figured I would run it past people with some experience (or have pictures of this setup). I dont want to have the mounting locations break in case of an accident but dont want to waste my time and end up screwing my self over.

Thanks!