Looks good! Ya Sumitomo's are notorious for being cheap and ineffective.
I dont know if you saw the check your axle nuts thread but the nuts were discontinued by Ford and replaced with this:
Looks good man.
I have an IRS with 410 gears and all the MM upgrades and am thinking of getting one with 355 gears in it.
I don't like the 410 gears AT ALL
Old nut is only at 95 ft lbs? Needs to be 240 minimum. I do 250 with red loctite. Thats definitely interesting with the double nut haha but I would double check the torque on the old nut. It may not be completely seated
Can you mark the nuts with some hivis assembly marker, yellow, white etc? Quick glance to tell if they're coming loose.
Curious. Do you not like it because it's a 4.10? Or because it's a 4.10 in TOO high of a horsepower car?
I have read where a lot of the Cobra guys don't like the 4.10 because it's too much power for such a short gear. Granted you are speaking of a Cobra.
However, if your 4.10's were in an N/A GT with a third of the power, do you think you would have the same feelings toward them?