Header question

Are the subframe connectors really necessary? I don't plan on going overboard with the thing.

Unless you don't mind having your doors out of align, It's all about torque and torque equals twist. The connectors are cheap insurance. You don't need to come up through the floors with your build or go to torque boxes, just some 2"x3" tubing, 4 pieces of flat plate and weld her up. Make sure the weight of the car is on all 4 tires.