You are going to pick up about 1/2 point compression right off the bat. You probably will have good piston to valve clearance also.

I shaved my Mag heads .020" before installing them on my stock '74 360 short block. And my cam is adv. duration of 268/285, and lift at .050 is 220/236 installed at 108* intake center line and I still had plenty of valve clearance to the stock dished pistons . I was also able to use the stock wimpy Magnum beehive springs for break in and had no problem with coil bind. Make sure you check this. Swapped in the proper springs after break in, and the cam is happy as a clam.

You'll need to determine what RPM the new build makes it's peak power, then adjust your converter and/or rear gear and/or rear tire size accordingly. Ideally you'd want your cruising RPM's to be higher than the stall RPM. If your stall speed higher than your cruise RPM's you'll generate a lot of transmission heat unless you have a high quality converter. At any rate, a good auxilary trans cooler is in order if you don't have one already. If you could get a 3.55 gear it would help get the B out of the hole quicker.