Are you planning to use a modern speed controller?
If so, forget the resistors!
If you want to recreate the old switched-resistor system, you will need several very large and high powered resistors and it will cost far more.
The asbestos mat with the switch studs was itself a large wirewound resistor with multiple tappings - and with the original design some parts could have happily run near red hot, but you cannot use conventional resistors in that manner, it would need the open wire resistor unit recreating using nichrome wire on a heatproof former.
Using conventional power resistors that have a finite operating temperature limit, the resistors would likely take more space than the motor...