Those are the generic Chinese Air Gap manifolds that I spoke of- they are sold under a number of different names and vendors- search for your best price. They fit both LA and Magnum heads, so if you do go the Magnum route down the road, you don't have to hunt down another manifold.
They work well, but aren't anything special other than what you'd imagine they are: a decent performing, low cost street-oriented option.
If you're not in a hurry, Speedmaster usually offers "Black Friday" deals of up to 50% off, otherwise these guys have a respectable daily price:
For 1967-2003 Small Block Chrysler/Mopar 318 340 360 Air Gap Intake Manifold | eBay
Oops- I just noticed that the one you showed was even cheaper by a few bucks- good find!
