J. C. Penney Co. expects to complete its move from New York by July 1, several months ahead of schedule, the retailer said. Chairman William Howell said he expects about 60% of Penney's 2,200 top managers and a smaller percentage of the 1,600 New York-based non-managers to move when headquarters shift to the Dallas suburb of Plano. Howell said 93% of the more than 150 top managers have accepted Dallas assignments and some have already moved. Next month, the company will begin making transfer assignments to other employees, who have 60 days to accept or reject the offer. The move is expected to cost $140 million, which will be charged against 1987 earnings.