(This pertains to the US & Canada only) The Mitsubishi engine was installed in the 1987 & 1988 B2600's only......the 1989 B2600i has the Mazda G6 engine in it......with a slightly different throttle body, distributor, and ECU and they're associated wiring.....than the 1990 through 1993 B2600i's.
I haven't seen a pdf version of the earlier B2600 trucks out there......only the book form. You can look on ebay and usually find a paper manual for the 1987 or 1988 B2600's.