What size MILLING MACHINE for building a 4-8-4?

[steamboy1975]

 My father has a 10 inch lathe, he would let me use for the project but I am in need of a milling machine.       What size milling machine would I need to build a 4-8-4?  Can I use a Sherline Mill?  My game plan is to build Robert Maynard's Clishay first to get an idea and basis of what I am doing, and then to build a 1 1/2 inch version of the Norfolk 611.


               Thanks guys for your help with these questions,  I am fairly new to this stuff.