I was told the later ones were different to accommodate the alternator!
Yes they are different, also the pushrod length is different. I can't remember which is longer.
The generator is longer by 8mm i think
There is also differences as to what is the in and out holes. Some have arrows. Some are in on the bottom. Some on the top.
Real pain if ya have to find out by experience 
yep, old genny style has longer pushrod & recessed actuating lever. alternator model has shorter rod & protruuding lever.
as to what way in & out. huff & puff on the pipes or just hookem up & swap if needed.
right one is old style genny, left is short stroke alt pump... or am i too pissed...
yep pissed
left is long stroker generator & right is short stroke alternator
on mine you were right the first time... or maybe i'm not pissed enough.. 
eim pissd enoof. I duno wot ye torkin abut ^&*
hwoop hwoooouk BLLEEAARUUUGGHHH
:puke
Then I bought the wrong one
Can I use the later one on an early engine and
use a short pusj rod?
yep, go to wrekers & grab one
(not pissed anymore)