Brother,
IMHO I have done "Alteration" to my CD70 and used 125cc head Cylender, weight, crank, Clutch Bos, CD200 Carburator... but was never happy by its performance.
It had accelration some time even better the CG due to light weight, but it never touched hunderred on its own, I only saw it couple of times actually hitting accross 100kph on underpasses or while comming down from bridges..
So its pretty useless to alter, all you will get is good accelration but if you had dreams for top speed then its a harsh reality.
No doubt people are now switching to Pit bikes engines becuase a complete engine is a well balanced in all aspects, local mechnics cant "engineer" and rely mostly on hit and trial.
Hope that helps.
PS. Stay safe recreational activities are pure love but do it carefully with all counter measures.