I have a 73 400 YX motor with 7k3 heads and a 4 speed manual trans. Looking to up the power a bit and have seen a lot on 6x4 heads, even found a set of them locally that are rebuilt. Any input on if this would improve my overall power output.

I am also looking at adding power disc brakes to the front and would love to hear what people think if they have them or not. My car currently has non power drums on all corners.

And the final thing I am considering is to change my rear end gears. I have been driving the car often since I just got it and plan to continue to do so, it has a stock 10 bolt rear end and does ~3000 rpms cruising at 70 on the highway which makes me think I currently have a 3.42 rear set. I do not plan to drag race this car just a cool cruiser so any input is appreciated