Need a Good Website Calculator for ET to HP

Rock 'em Sock 'em Robot said
I know, that is what is strange. I will take 'er to the dyno I guess. Last dyno run said it was 397.8 at the flywheel, hp. Torque was 476.2 What's the difference?

I think the difference is the 3:23 gears. They are very tall for dragging. The website most likely assumes 4:11's or shorter. What do you think?