I have 1970 Duster drag car. Only thing original is part of the frame rails. Way beyond making street legal. I would like to buy just the title for a 1970, 1971 or 1972 non- Missouri Duster. I think race cars do not need a title but I want a title. Any help/info is greatly appreciated.

That would be fraud, imo.

Depending on the State, you should be able to get a title; may be as "new construction".
I was able to title a drag car that still had its original VIN & body, but it was tagged as a non-streetable car - because it didn't have a windshield wiper system - which was fine by me.
I had to do a title search for every State it had been owned in, and found it had never been titled since new.
Took a little time but wasn't a big deal.
In today's environment, having a title is a good idea if at all possible.

which frame rails are left on it?
I was trold by a CHP years ago that the Mopars back then had the VIN number stamped on the inside of right rear sub frames even with the gas tanks
I would check on Hemmings to find one If you can't find one listed place a wanted add with it being a race car and not for street use How about local junk yards in your area selling you a title for one?

Applying a title/Vin to a car (chassis) other than the chassis it came on is a federal offense...might not want advertise your efforts especially on Hemmings.

That would be a Felony, & state laws can apply also.

Do it the honest way, apply to your local DMV / BMV for a state assigned VIN. Your new title with have that number on it.

Pennsylvania has a method for something like that. paperwork, then an "enhanced inspection", and if it is accepted, you get a state issued vin tag and reconstructed [or whatever the Harrisburg "geniuses" decide to put on the] title.

Re-reading this, and the OP's car being a vehicle with apparently no VIN, let me clarify my response:
That would fall under "new construction", or whatever the OP's State would assign to what's essentially a custom vehicle.
I would NOT use another vehicle as a VIN donor !