My advice: Do NOT get a tube-framed seat, like the Sparco Junior or Corbeau Clubman or Corbeau Forza. Putting a seat back brace on it is not easy and nothing looks like a good option if you even do try. I highly suggest that you spend as much $ as you can on either a fiberglass/carbon fiber shelled seat or an aluminum Kirkey or similar. DO NOT get the Jegs aluminum seat.
At Buttonwillow an ex-circletrack car was going/failing through tech with that Jegs economy seat and Jay just grabbed the top of it and leaned on it and bent the top over 90degrees. There is no channeling or reinforcing in that jegs (or economy) drag seat. Spend a bit more and get a Kirkey or Ultra-Shield if you want to go aluminum. Notice the difference in the channeling (grooved like a floorpan). Quality of design and construction makes all the difference:
Sliders are ok, but get the kind that double lock---each slider has a locking mechanism on it-- miata seats have them that are connected side to side by a cable and you can narrow or widen the width as needed.
Most modern cars have double locking sliders now, too. OR just buy this one:
http://www.ebay.com/itm/Universal-Seat- … vi-content
You can put a 1" box down through the floor to lower your seat mouting if you need the height. The other option is to recline the seat to get head clearance. Also, when mounting the sliders to the car, if you mount the front of the sliders higher than the rear, as you slide the seat forward the seat will also go up so shorter drivers can see over the hood, and taller drivers go lower as the seat goes back.
Just mount it securely using grade 8 or equivalent bolts. If you can tie in your seat mounting into your cage somehow, that would be ideal.
(Disclaimer: I really have no idea what the F I'm doing or talking about and, in fact, have had a car that I built fail tech because of my seat mounting.)