Cam question for my 4.8

[Dan Neumann]

Ok, I'm getting ready to replace the cracked Castech 706 heads on my 2000 GMC Sierra 4.8 with a set of reconditioned non-Castech 862 castings running Chevrolet Performance 12499224 springs. While doing so I'm going to change the cam/lifters and probably timing chain. I'm looking to run either the Comp Cams XR259HR or XR265HR cam. My question is I've been told I should shave a little off the heads for starters. How much?? Would I need new pushrods then? Also which cam would you recommend for good performance but will pull my 18' bass boat often? Initially I will be running the stock exhaust manifolds but plan on putting long tubes and a full mandrel bent dual exhaust on it not long after. I also will be running the stock converter initially but an not against going to a slight higher stall if it's recommended. The trans I had rebuilt a few years ago and it currently has a corvette servo in it so it's got a real snappy 1-2 shift. It also has a 3.73 gear with an Auburn limited slip unit. Stock size 15" tires.
Is a new oil pump recommended or will my stock one be fine? I was told I should replace the pickup O-ring though. TIA