I'm going to assume your tranny is full automatic, correct?
If so you would have to rev it up slowly on the chassis dyno at part throttle until it is above 4500 RPM in high gear probably to make it not down shift and then slowly floor it and have them start to record the pull once your at WOT
I spent some time on a chassis dyno with my race car several weeks ago, I would rev it up to around 5100 RPM at part throttle in high gear (Powerglide) and the dyno operator would give me a thumbs up when he was ready to start the recording and I would floor it
I had a 7200 RPM chip in the three step and didn't think about that until after the car was off the dyno
have fun, learn some more