I would run the motor as-is. I have an 89 TBI 5.9 myself and will be doing just that. It's a jasper rebuild with something like 1500 miles on it so that's why I scooped it up, but then again I am not looking for performance.
If you want 400 HP then I suggest you get a magnum motor and follow the low buck build that Mopar Action did last year or year before.