Back half regrets?

Is that a factory aluminum block? It's my understanding they aren't really strong. I know a few local guys that are running boosted LS engines and they all run iron blocks. There are several reasons you see a ton of mustang bodies in the fast small tire classes, but the biggest is that they come with what is essentially a factory four link rear suspension. Adjustable bars for them are just a phone call away.
If it were mine and I was planning on putting big power on it later I'd go straight to a four link and save my self some headache and money later. Also I'd go with a good 9" rear, used aluminum bolt through cases can be found for reasonable costs and as you step up the power you'll need less gear. My buddy built a single turbo 5.2 LS in a early 90's Mustang for his teenage son to drag race and it runs 5.60-.70"s (1/8) with a 3.50 gear on Pro 275's.