A Scratch Bracket will be a must ...
If you do mount them in the original stepped down location ... the back seat will be too close, no foot or leg room ... picture a 6' guy in the back seat of a Camaro
You will have to mount them up level with the back floor and make the bracket for the front portion.
Too far back and its like climbing into a Limo
And Welcome to the forum ...
Do some searches and you will find where others have done what you are talking about, me included before the current WIP.