closed chamber vs open chamber

I just purchased 440 Source heads for $1064.93 to my door.Nice folks on the phone, surprised I usually do not expect customer service these days
I was going the 516 route but by the time I gave them a clean up, checked them for cracks, seats, milled them, valves?? I was to close to the 440 stealth heads in cost plus I am shaving 50lbs,
. I am going to shave them .025 to get my Compression up a full point and swap over my springs, new locks and retainers

Thanks for your help