Gas Mileage... Wow that is a line...lol. If anything it will eat a bit of power...lol. in the turns anyway...lol. Well I see where your going...BUT you are restoring a Muscle Car. If you start cutting corners on the resto too far you will regret it. Think it through and do not rush the job.
It is a good deal for a 12 bolt chevy rear 300.00 ...WITH posi!!! I would grab that ..BUt makes me wonder... WHY? I hope it is all good or are you headed for another headache.
Please watch going too cheap as you might be setting yourself up for more expenses down the road too. Jim