I decided to use a Mac shorty header on my build because it's very simple for my application and I should be able to see some gains when it's paired with a 2.25" exhaust (and no catalytic converter). I couldn't find any decent photos of it online so I decided to take some myself. This post isn't a rave review to over-glorify the Mac header but to simply compare an aftermarket shorty to the stock header. You can probably find similar specifications and quality on many other aftermarket headers and that's why I think this comparison is worthwhile for those who are interested in upgrading.
I was able to find a Mac header for an affordable price on eBay (Slightly more expensive than Pacesetter or OBX). It included a copper gasket and was finished with a polished ceramic coating. When I first pulled it out of the box, the ceramic coating looked a little hazy (probably due to some left over residue from the coating process) but some mothers aluminum polish was able to quickly clean it up to a better shine.
As you can see from the photos, the Mac header is a bit larger than the stock manifold. The Mac header's primaries have a 1.65" inner diameter while the stock is about 1.4" (It's been a while since I've measured the stock manifold so correct me if I'm wrong). The Mac header's welds appear to be good on the flanges, as well as the slip fits on the primaries.
The collector size on the Mac header has an inner diameter of 2.5", which is larger than the stock header by .25". The inner weld on the Mac is also not as profound as the stock header which may help with exhaust flow.
The difference in the collector probably helps with flow the most. Ditching the clam shell style of the stock header is probably the biggest improvement for flow.
Overall, It looks like it will be a good performer. I hope this helps people who are interested in upgrading.