Somewhere in one of my threads there is a photo of the engine support I used to hang the motor so I could drop the K frame without pulling the engine, was super simple, and made putting the headers in super easy, I also changes freeze plugs at the same time. The guys at FF suggested I didn't need a sector support on my 73 K frame, just weld some gusset's to brace the box mount, I did that and there is no flex
From what I've heard, the sector support does a great job, that for the average guy, you don't need to gusset the K-frame if you do it. But welding up the K-frame is the way to go as it adds strength to the entire front end. But if you can, do both!