your gonna have more trouble with your current way of thinking than you might think..
header flanges are easy to make, sure it takes some time... but it will be better for you in the long run...
every time you get a gasket leak, do you wanna spend the money to buy 2 sets, or spend the time making gaskets?
skrew that.. IMO.
get a set of flanges from world to fit your heads, or make them..
3/16" steel will never warp on you. and no matter if your cutting aluminum or steel, its the same amount of work to make either a flange or a aluminum gasket...
as little parts as possible... thats what ive always been taught!