This is copied from the TXDOT Motor Vehicle Title Manual, chapter 25 Reconstructed Assembled Vehicles, page 10.
"MOTOR CHANGE
1. If a new or different motor has been installed in a motor vehicle which records the motor number as the identifying number (all 1955 and prior model motor vehicles, except Ford vehicles manufactured since March 31, 1932), a corrected title application must be filed...
...Other requirements are as follows:
A. The application for the corrected title must be supported by evidence of ownership (title) to the vehicle, a bill of sale to the applicant for the motor installed, and a pencil tracing of the motor number."
You haven't stated whether the title is transferred already or not but I see no problems.
