vintage air and overheating issue (LS engine)

[rodstored-72]

well I had a shop look at it & it appears that the head gasket might be the issue. there is no indication of a leak into the rad. the engine stays cool until you switch the AC on or under a load (my luck!!) the shop feels the driver's gasket was not installed correctly - fairly easy to install upside down or backwards??? and would still "seal" right, but would block passages and keep from good flow??? so i guess now back to the engine guy for warr. work... aarrggg