scott goplen, richland center, WI, 68 ply cuda 340

I put a set of headers on my 'Cuda and they leak and leak. I exchanged the summit ones for Hedman, I bought 3 diff sets of gaskets, they leak between the head and gasket on most ports. There seems to be a pinky sized hole under each exhaust port and that may be the problem, but I can't figure out why the leak. I found a 255 and a 23 stamped under the rockers but cant seem to figure what heads these are they are suppose to be mopar swirl port type i know they arent magnum these have 5 bolt covers.i havent seen the holes under the ports on any other heads so i dont know whats going on here. Any ideas on what heads these are and to why they leak so terribly?