Is the 1983 Caprice Classic 305 a 4 bolt main?

No There's no factory 4 bolt main 305's Factory 305 4 bolt mains did exist. I have one, came in a 1983 G20 Chevy Van. AnswerThere were none ever produced...no reason to either. ANSWER is YES They where produced BY GM Canada St. Catherines, Ontario they are rare as heck made for service trucks/vans