Hi firstdrive,
I went through the same situation. However dealer has given me the official letter stating allocation number, is in transport & will be delivered to me on approximate xx/xx date.
I was also hesitant to make full payment & told them that since i've my payment ready & money will be transferred electronically to your account on the same day only after it arrives at your yard after doing physical inspection. After lot of discussion sales manager agreed.
After it arrived, transferred the money on the same date & got delivery after 2 days after finishing RTO formalities.
As you are not taking any loan & money is ready, try to convince them.
Cheers.