Mukesh Kumar ji,
Your ideas and views of converting from excise Dealer to excise Manufacturer for the purpose of availment of cenvat credit that you are losing as dealer, is perfectly Legal and Correct.
Yes you are eligible for such conversion. First of all, you have to surrender your excise dealer registration and thereafter you have to apply for excise registration as Manufacturer of goods, after which you can avail cenvat credit on all the inputs, input services and capital goods used in the manufacture of finished goods.
Further, there is also one way to the issue – You can carry on as excise dealer and simultaneously apply for excise registration for manufacture of goods and become a Manufacturer.
In other words, you can be both Dealer and Manufacturer and can hold both the Registrations.
You may seek further guidance from the Excise Division/Range office in the matter.