Thanks for the detailed reply.
So now the question is "Is it possible to build a complete chassis ourself and get it registered". This can be done by seeing detailed photos or drawings of chassis of other manufacturers. I think the chassis can be built but wont be that perfect.
Also please intimate if we can place the body cabin of some other vehicle on the chassis manufactured by us. It will be possible, but will it be legal?
Awaiting for your expert opinion. Thanks.