GST for Contractors

Yes.... you can .
But Need to be registered under new composition scheme prescribed in Notification 2/2019 CT (r)
Limitation : Turnover shall be below 50lac
: cannot deals in supply Non Gst
goods
: need to charge 6% on turnover
without ITC
So I dont think the scheme will be feasible for your business & moreover check it from railway that whether composit dealer can apply for the contract.

Thanks Pankaj Rawat sir .

If I registered as regular dealer what will be the frequency of return ???

Turnover Below 1.5 Crore .
monthly : GSTR 3B
Qtly : GSTR 1

Turnover Above 1.5 Crore:
Both above return Monthly