Mac 1 3/4 shorty

[onlyme]

Anyone seen there 1 3/4 shorty for gt40p heads, im just a bit curious what I dont get why offer 1 3/4 for these heads but not for afr/twisted wedge and such since they flow much better cfm.What would be the benefits from these headers unless the heads were ported or used on a supercharged or turbocharged motor or possibly a stroker?

http://macperformance.com/store/category.cfm?SID=3&Category_ID=794

mac part number 54134