I also had the flex pipes but still cracked after only 200000 miles. Wonder if the 3inch spring lift I removed had any thing to do with it. priced a ex manifold from chrysler at around 430.00
Gale banks makes one (yeah the diesel guy) 400 (430 IIRC?)series stainless; most are "only" 304 grade; I welded mine up like 4 years ago. still running the orig one on my 97 has held up fine since I repaired it.
if your looking for an after market you can also go to clifford performance they make a nice after market ex manifold and an intake to match but kis is a little pricy.