I know about fontgdos drivers, but not timeworks drivers.
Fontgdos drivers can be modified with the printer.acc accessory from the fontdos distribution.
Failing that, if you are comfortable with a hex editor:
- make a backup copy of your fontgdos driver
- load this backup copy into your hex editor
- look for the string "_FSM_HDR", it should be near the end
- count 40 (decimal) bytes further on
- for letter page size, the 16bit word there should be 0000
- change this to 0002 (for A4)
- save changes
This image shows the 00 02 value for A4 pages just above the 4B 4A in the DESKJET text:
Hope that helps.