Swapping out iron J 202 heads for aluminum

You'll definitely feel/see some kinda improvement. As the cam grows..the more itll show. Atm it's in the range of a j head..that if well worked will make great power and run with the .100-.500 lift flow of the shocker.
Even if the heads flowed the same 'which they dont' they're lighter weight and the exh port is a lot more efficient moving more out begining at far lower lifts than the j heads.
J head exh port isnt doing much past 190-200 cfm...mostly 190's, Ported.
Could be part throttle just gets better... the kind where you just barely tip it and it accelerates and revs up faster on it's own.
We dont really know though... being I ported my own j heads and they are 186cc and flow in the usable 270 cfm range. I'm saying "ported " can mean 230-290 cfm and any volume in between and up to 190cc.
I have never seen one bigger than 190. They would have very thin bowls at that level.
I guess one thing to consider is that recently somebody got a set of these Shockers and put them on their own flow bench and they claimed that they did not hold to the numbers advertised. The numbers could easily be met by a j head or exceeded...from what I saw.
So everyone is pretty much on the money, hard to say.