nipple drains and check valves....mid 90s V4

I am going to finally start putting my 1997 V looper back together... I have a 1995 version as well, that I look at for help to see how things go. I know that both of the nipples on the bottom half of the crankcase are rusted through... looking at the parts supply, they are listed different for 1995 than 1997... the later model has a check valve underneath the nipple... the 1995 version just shows a nipple(90 degree). this is what the 1997 block looks like.: , does not seem to be a check valve under that nipple.....but I haven't tried to unscrew it yet. does anyone know why they have check valves listed in the 1997 parts and not the 1995 parts...and does it make a difference? the nipple is the same part #, the check valve isn't used on the later models....bob