Hi Bob . . .

Based on the parts wiki over at the GM Heritage site: Parts and Accessories P&A 30 October 1962, there appears to be no distinction between a 235 and a 261 pan. However, there are differences between the mid 50s version, later 50's and early 60s. You are looking for part number 3760422 which is specific to '58 and '59 models.

happy hunting
stock49