need a little help on building my rear

There's a difference between 'street' and 'I wanna cruise at 70mph for 2 hours'.

I would go with a 3.54 in that Dana if you are seeing street and track. Get a cam that will make use of that gear and your cubic inch displacement combo. Luckily you have a 4 speed so this allows you to get creative with cam choices.

With the right cam consistent 12.5's* are possible with the right intake, headers, and TRACTION.

With a 27" tall tire you will do 60mph at approx. 2750 rpms.