Luke,
i used to have a fixture for my little shop press to put runners into so i could square/rectangle hem. If i can find it ill take a picture of it maybe you can check it out and make somthing similar to square those up, you shouldnt have to use a torch and i try to avoid the heat as much as i can..
Also do you have and "10 to 1's" from MAC?
These, they work great for making gougeless bends on the edges of the tubes.
I also on 1-3/4 and 2" primarys that use Square ports i will build small sections of straights that weld to the flange then the bend. I machine a solid bar stock of aluminum to fit snuggly inside a straight section of tube then bend the edges into the square pound out the alum mandrel and it keeps your tube perfectly round to weld the bend on to it.
I have built dozens of Domestic turbo headers, so this stuff is natural to me, but i have a hard time explaining how i do stuff or why. My biggest Suggestion to anyone getting started, the best way to get the best results is to get organized, get your work area cleaned up and all the tools you need in order, the more organized you are the faster and happier you can work. the better you clean your materials the better the end result. Right now my Fab area is a complete disaster area and i cant get any work done fast, im taking a half day tomorrow to clean up the shop and mainly my fab area and organize all my materials and tools. ill get some pictures of my setup, i dont have alot of baller tools, i stifle my self because of it, but i also like to build my own tools as i need them.
Jon