Ponys to Cobra's

The weight isn't a problem. THe tire and wheel combo now is probably a little lighter. Your ET could be hurt some considering you probably now how lower profile sidewalls, which are great for handling, but the last thing you want for drag racing. They are hard, and don't flex. I bet it looks good though!
 
stang8urmprt summed it up pretty well. From 16's to 17's, it won't be too much of a difference though. Put drag radials on the new 17" rims and you'll be further ahead (in terms of straight line traction) than rolling on 16's with a regular radial.