How is your dipstick attatched to the engine? Did you reuse the bracket for the H body one, on the new W body one? (you did put a w body one in right?)

When you hit reverse it may flex out some, and then snap back into the header. Maybe try putting something on what you think may be hitting it, and seeing if it transfers to the headers. Might be best to do this cold..

Don't use hockey pucks for suspension lifts in coil over systems....bad idea.....Kinda funny to see one get pinched out and shoot through the fender. Looked like someone took 12 gauge and put it to the inside of the fender and pulled the trigger.....We never did find that puck......