You'll need a stereo lead (not included) for full functionality - the JCM 800 seies were quite basic with simple channel switching and reverb is on/off.
Vintage Marshall JCM800 2-Button Footswitch Pedal - Reverb & Boost
Vintage Marshall 2-Way Footswitch Pedal (Channel & Chorus)
Rare Vintage Marshall 75 Reverb (Model 5275) 1x12 Combo - Spares/Repair - Read!!
VINTAGE MARSHALL LEAD 12 1 X 12 GUITAR CABINET - HEAVY DUTY 100 WATT AVT112 UK
Vintage Marshall JTM C12 1x12 Speaker Cabinet Celestion G12 Heritage
Pair of Vintage Marshall JMP Amp Amplifier Head Feet - 1970s - NEW / NOS