welcome to the site! I am not sure either style is necessarily "better" than the other. I had a Willys wagon with the tailgate (similar to the clamshell on the burb) and my 59 Suburban had barn doors. Each had benefits. Barn doors were way nicer for loading groceries, but the tailgate was nice to drop down and put a camp stove on or use as a table for whatever. On the Willys, the tailgate was rated for 500 pounds!
AS far as the brake kit, I am assuming it is one that goes on the frame where the stock master cylinder goes and it will hit some linkage. You might need to call the place and find out. Maybe you can just move it back a few inches?
