I use them in my l/m motors.I've never dynod them back to back but I wouldn't expect more than single digit hp numbers if that.They load the crank different and are suppose to be easier on the bottom end.
The 4-7 swap, although relatively new to racing, is nothing new for GM engines. It's simply the firing order for the old Oldsmobile engine introduced as a 303 c.i. in 1949 and like RCJ said it's doubtful that you'll see much, if any, difference in horsepower. I'd direct my efforts to something more substantial.
Some people feel like they are a little bit "smoother" on the track. Take that for what it's worth since on-track feedback can be subjective to other variables.
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