The Plexi 68 is the Bass Model so the 1986 (less gain, more bass) The Plexi 69 is the Lead model so the 1987 (more gain, less bass)

Hi, The Bassman is the same model of JTM45. The difference are : -12AY7 on V1 instead 12AX7 -NFB resistor 27K on 2 Ohm tap instead 16 ohm tap (you can use 56k on 8ohm tap or 75k on 16 ohm tap) -A cab with 4 Jensen 10" speaker instead a head and a 4/12" Celestion speaker Thats all For the JCM800 2203 is the same of 2204 : a 100W head and the 2204 is a 50W Head