Re: 505 Stroker Build
25.52% parasitic loss through the drive train lets me guess you have a 4,200 RPM stall converter and a nine inch rear end.
The increase in initial timing over the 496 and the loss of horsepower indicates that this isn't a very efficient combination. I am of the opinion that your heads are a little on the small size for an engine with this displacement (I probably would have gone with the 315 cc CNC AFR head for this size motor; if I were buying new heads).
I am also assuming you increased the bore on your old 496 build as opposed to going to a longer stroke crank. The thinner cylinder bores also contribute to your horsepower drop as you are loosing more heat to the coolant (which will put a further strain on your cooling system). Cast iron is a lot worse at conducting heat compared to a metal like aluminum, but as you thin it down the then the heat can flow through it at a faster rate as the metal thickness decreases. It also becomes more flexible which will upset your ring seal.
My final comment is on the carburetor. A 4500 series carb makes a BBC a lot happier than the same size (cfm) 4150 series carb. People say you can not run a 4500 on the street (I did it for years), but I would point out that most cars built to this level are not considered daily drivers. I prefer the added performance over the look of originality with the smaller carb throats with a shinny open element air cleaner and a 396 decal on it.