Your statement says 24" in front of the rear end centerline, but do you mean 42" because you would almost have to be in the same holes with 21" 4-link bars? If it is indeed about 42" then that is about right for the HP.
What is your ET and your MPH and that will help decide if the 60ft is slow?
It sounds like you might have some issues with the front suspension not letting it work and that is causing you to have to beat on the rear tires. What front springs do you have? On my car the 60fts were slow until I put some softer front springs on it (went from 400lb/in to 300lb/in on my front struts). I used to have a Nova with ladder bars with the engine moved back and stock front suspension, that I couldn't get it to hook or pull the front wheels until I changed the front springs over to the Moroso trick front springs.
Bill Mitchell