340 torque converter...

Get a 3500 stall converter and don't let anyone talk you different. If you want performance like an original 340 car . Remember an engines torque will also determine the stall also. If it stalls less then 3000 it will be a pig from a dead stop. A stock 340 will stall at about 3000-3200 with a 3500. All factory 340 cars I owned would brake stall between 2800-3200.

Most all the plow trucks came with a low stall 2200-2600 . I don't believe your building a plow truck.