No offence or discouragement meant at all but that bike looks a real load of trouble man.. One can't really tell for sure from these pics but it looks like rust has eaten through just about everything.
The two most important things - frame and engine look to be compromised. You wont know until you open up the bore but the outside looks pretty rusted up. Check the frame completely to see whether its just surface rust. From here it looks like its been eaten through at places.
These are not the sort of things one should get tinkered. The mud guards, rims, even tank perhaps. But not the frame and engine.
If they aren't ok (and I hope for your sake they are) then you've got a real problem. You don't get original piston-cylinder kits any more. And if you do they cost a BOMB! The guys who have spares are enthusiasts who are unlikely to part with them.
It also appears that rust has gotten into the gearbox and the points system, not to mention the tank and the rims though (tank and rims are the least of your problems 'cos you can lay your hands on used ones albeit costing a bomb). Gearbox and points you might be able to get but you'll have to really wait it out and chase scrap dealers for it. Also, don't use aftermarket pipes. They really suck. Mufflers you can get local ones. Anyway, their purpose is only to keep the noise down.
I wouldn't advise a CDI. This is a classic bike not a commuter and you should try and keep it as such (when you get to that stage). I'm sure its possible to fit a CDI through Jugaad but jugaad on an old bike is never advisable.
Basically it looks like you're going to have to re-build the entire bike from scratch man. It may as well be a new bike for all practical purposes.
Did you get papers along with it?
As for the rear shocks not being original, I wouldn't say that. They look like they're just missing the cups. A 1970 would have the thicker shocks, just like the Yezdis which followed.
The rest has already been pointed out by sixspeedtwin. Though I must confess I didn't know the pipes were different

Cheers
Rahul


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