X heads that flow 250 on 416

I have been looking at my 416 short block for some time now and life keeps throwing BS @ me so I an unable to buy the heads I want at this time. I do in Fact already own some Fresh X heads that with some port work that flow 250/172 @ .550 Im very tempted to just say screw it and use them w/ A comp XS282S cam .520/.540 244/252 @.050 in which I already own as well. Any thoughts as to what my loss in power will be. The X heads are 68 cc. so that will also drop my wanted compression ratio from 10:1 down to 9.7:1 My original plans were some alluminum heads that flow 275-280 and a bigger voodoo 30200741 .546/.566 243/251 cam. I want to start driving this thing already, but will not be reaching my 500/500 hp/tq goals.