This is compiled from various sources, mostly from discussions on the Hobie forum. Changes are generally listed by year, but that is a generalization; they didn't happen specifically at the beginning of a new model year.
Major changes were in the '82~'85 range (adjustable rudder castings, mast rake, comptip) and mid '90s (integrated tracks, tiller connectors, cast gudgeons), although you can see from the list that improvements came every few years.
Cleats varied over the years and I don't know how much; the main change was from steel-toothed jaws to verious aluminum jaws. Cleats can be from Seaway, Ronstan, Harken, Holt-Allen, or maybe even some other company.
Quite a few different rudders were available over time, but plastic was always standard until the mid-2000s when the EPO2 was used. Matt Miller and Matt Bounds have a good listing here.
1969 - Introduction. Original main traveller car was sliding metal plate, original mast base with hook
Early '70s - mast base (and step?) changed to remove hook
1972, '74, maybe later - main traveler with rollers
1975 - introduction of black anodizing - or not.
1977-ish - 3-hole mast tang
1982 - Shorter shrouds, longer forestay, modified mast step casting to allow for more aft mast rake.
1983 - double-grommeted rear tramp lacing
1983-ish - jib blocks moved to pad on crossbar
1984 - weight reduction 340 to 320, red adhesive
1983 or 84 - Adjustable rudder castings
1985 - Comptip and new main halyard, reef points removed from main
mid-'80s flush boom vang fitting and then removed
mid-'80s clear anodizing ended
Note: current surface-mount main traveler track from Hobie is deep, to make use of the newer traveler car design.
mid-late 1990s - updated bolt rope in sails, eliminated tack and clew plates
late 1990s (maybe 1996 with long-lock gudgeon screws) - die-cast rudder gudgeons
2002? - recut jib. 5" longer luff
2003 - return to original corner castings (per note in the 2003 parts catalog) but went back to "new" casting later. Still, some boats had riveted blocks for a while.
2004 - upper main sheet block changed from H2604 57mm triple to H2640 40mm triple
2004 - revised mast base and step. Change to improve rotation with more rake and hold mast bearing chip better.
late 2005 - roller bearing jib traveler (same basic wheel design as the main traveler).
2004~5 - EPO2 rudders standard?
2009 - shrouds shortened slightly to 18' 10.25" - bridle lengthened to 3' 9.5"
May 2013 - EPO3 rudders standard
1Read the linked threads for details. The integrated track was introduced at some point in 1994 and the new corner castings weren't necessarily introduced on the same boat. Those tracks were too shallow so they were deepened for 1995 and the brass-wheeled main traveler car was introduced. I'm not sure what the jib car was for the shallow track; apparently it looked like the later one but must have had a thinner flange.
2The H194 was publicly discontinued by Harken before 2013 and exclusively supplied to HCC, who is still selling it as of 2019.
The jib was reshaped at least twice. My 2000 jib did not match my 1978 jib and there was another change after 2000.
At some point - probably '90s - the tack and clew plates on the main were replaced with Bainbridge D209 Inox cringles.
2000 (sail set 104691) jib: 178" leech (to middle clew hole), 183.5" luff, 65.5" foot (to middle clew hole).
Sailrite says 192" luff, 189" leech, 69" foot. They may be measuring the foot and leech differently but the luff dimension sounds like it must be the 2002 version.