for tunig contact 60-1ek, or 99b16si, depending on which route of mangement you go.

as far as D series problems, there are only a known few.

-overheating
-headlifting
-slow......J/K

that should be it, make sure you either buy headstuds, and rod bolts, and that the head and deck are completely level, i have no idea if the motor is assembled or disassembled. but depending on power goal, yo may not run into any of these. i know most of this occurs at about the 300hp level