Holeset turbos are good, but the one you have is on the large side. It would probably work on a 351-408, but a 302 will need a bit of rpm to get it spinning up. Usually something in the .90 range on the turbine will be a good cross between performance and driveability.
Are the Powerstoke's turbochargers different between the Econolines and F-250s? I hear they spool up slow, but a .83 wont....