Looks like they've derated the engine to around 180hp. Rad is under the pan with a decent looking diverging/ converging duct. Might be ok for 180hp but I doubt if it would cool it at 400 hp.
Bud Warren is claiming 488 lbs. for the whole shot on his site. He has a photo of the scale weighing in an LS1 at 375 and says the PSRU weighs 53 lbs. That leaves 60 for the starter, rad, alternator, governor, coolant, piping and exhaust.
If true, this would put it in the ballpark of a fully dressed IO-540.
I'd sure like to see an independent flight test done on Bud's RV10 with weight, fuel burn and performance figures.
I don't think every V8 RV10 would be have to be over 1750 lbs. empty but only time will tell as more are completed.