904 vs 999

It's in a '82 D150, slant six. Not sure it the truck got a tighter converter, but two things I do not like about the truck lock ups:

1. very unforgiving when going to reverse or drive, idle has to be low or it's more of a "bang" into gear rather than a "shift" into gear
2. Once locked up around 45 mph, it lugs the engine on uphill's or such.

Transmission is in excellent working condition.