I want to replace the RIGHT crankcase on my 2003 with a 1987 RIGHT side crankcase due to damage on my '03.  I have both the Clymers and Suzuki Factory manuals for reference and am gathering the necessary special tools.  The Clymers manual omit the "Crankcase Separating Tool" that is referenced in the OEM Manual.  Is this tool necessary?  Or has anyone had success simply tapping on the crankcase with a plastic mallet?  

I am grateful for any advice on this endeavor.  Thanks for reading!          

as the '87 and the '03 tranny are different, can't say the combo will be compatible.

and yes, I just used an angle iron and 2 opposing cover bolt locations over the crank to split the case.

While I'm not completely sure ,I checked out the cases and found that the bearings used on the transmission shafts ends that fit into the cases are the same for all years , which makes me thing your swap has a good chance of working .the other differences are the starter idler gear ,but the change was in the outside cover not the engine case so you should be good there . You may (don't know, forgot to look) have to change the speedometer drive shafts do to differences in the 4 and five speed transmission, (may be the same if driven off the same shaft as the drive pulley).