OK, here's the answer for adding a kickstarter to a 6 speed transmission. This does not apply to the CB450SC, see Notes
at the end.
First you have to use this gear PINION,KICK START for CB400N SUPERDREAM 1978 ENGLAND - order at CMSNL
available from CMSNL and Brazilian dealers. All the other kick start pieces are standard US model 1978/79 versions.
Next is replace all of the transmission and shift components with a 1980/81 CB400T, gear sets, shafts, forks, drum, etc.
Replace the clutch outer basket with a 400 basket, the others pieces are interchangeable between models. There is a different spacer behind the clutch basket that needs to be from a 400 also.
Replace the crankshaft drive gear with a 400 version.
Replace the neutral switch with a 400 version, you will lose the O/D 6th gear light. No choice there.
The 1982 CB450T transmission will not work and the 1978/79 CB400T 1&2 were 5 speeds.
For this to work on a CB450SC all the above applies with the addition of getting an offset front sprocket. The sprocket has to be offset outboard by 4.2mm to achieve proper chain alignment.
The shift rod from your current model can be used.