Time to pick a cam ....

I have almost the same motor in my '70 Dart Swinger; '72 340 .030 over, Keith Black pistons, compression is est. to be 10.2 to 10.5 to 1, stock X heads, stock crank turned 10/10, Performer RPM intake/Holley 700 carb, roller rockers, 904 with 3200 stall, 8 1/4 rear end with 355 gear....my cam is a Comp Cams 305/525...I think it's too much and it's actually slowing the car...I have had 2-3 people tell me I should switch to a Mopar purple 292/508 or 284/484...any suggestions??