Headers

I have a 91 Caprice wagon with a 350 from a 93 roadmaster. I am looking to put headers on my car but i was wondering if anyone has who has done this can give me more info. Will shorty headres fit do i have to modify the shift linkage or will they hit the firewall? Here is the link to the headers on summit.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=BIG%2D11108FLT&N=700+4294923429+4294908216+4294924928+4294840140+ 4294908194+115&autoview=sku

An info would be greatly appriciated.
Jeremy