I have this problem with every Hooker header I use. Other brands and fitment for other cars may be different, but you cannot even get a socket onto the rear plugs on the left side of a 73 Dart Sport 318 / 904 with Hooker Comps. One of the many reasons I love my TTi's is accessibility.
mine are on a 73 duster , 318/727 . I can get a socket on mine all day long. maybe you had an older set or something. I have changed my plugs and reset the gap numerous times without a problem.
