There's many unknown things about LTSPICE.

You can easily step the values of resistors, capacitors, voltages and other numeric quantities.

The .STEP spice command only takes a numeric list.

But you can also alias a number to a spice model using the ako: notation (A Kind Of)

then you can step the list of numbers if you wanted to step a transistor over 4 different values.

So in Dave's 2-transistor current source, he could set the transistor value to {Qx}

and add

.model 2222 ako:2n2222

.model 3904 ako:2n3904

.model 4124 ako:2n4124

.model 849 ako:ztx849

.step param Qx list 2222 3904 4124 849

and you would see the effects of changing transistors.

You can also have multiple .step spice commands, it will run them all, so you can step temperature over each transistor change.