The biggest difference in the earlier versus later Pucks is wheel size and windows
with a little difference in the onboard appliances. Early Pucks had 10" diameter wheels, then they went up to 12" for a while before eventually getting 13" wheels (with 135/70R13 tires
- which are almost unavailable in this country). I had to add some 2" square steel spacers between the axle
and frame to gain clearance for some 175/70 R13 tires
on mine. The later the Puck the better the window, mine are double pane and the left side and rear window both open, seals are better and more durable.
But early Pucks are very, very cool and probably a little lighter. The interiors aren't as plush as the newer ones but they can be easily modified and updated. All Pucks are nice - the older ones have had a few more years to deteriorate if they come from an aggressive climate.
And sometime around 1992 they lengthened the pop-up roof on the Puck by about 18" giving you a little more standing room inside. Compare my 1989 Puck - notice the raised roof section is shorter than my 1995 Puck