The 70 440 block I was useing made 785 hp and 690 tq. It was a 499. I used it race only and the block wasnt filled. I pulled the engine down every 30 or 40 passes or so. I did experience cap walk and used no girdle. I have since went to an aftermarket block with cross bolts. The engine makes a tad over 1000 hp and 780 tq now.
I'd say if you are racing your block and dont like maintenance, run the girdle. If your streetin and not into it for 9 secs or so at a time and launching at 5500 then you should be ok. But if you got it, run it. Like chryco says...good insurance.