[Amps] transistor matching question

[Dan Sawyer]

Good morning, I am assembling and eb-104 amplifier board. A couple of 
questions:

I have a set of MRF-150 devices to select the 4 required. Using a curve 
tracer I am able to find devices that have common gain within 5%, Is 
that close enough?

Based on measurements with bipolar devices, it appears as though the MRF 
150 also have the equivalent to emitter ballast resistors. That is the 
slope of the iv curve is noticeably upward in some of the devices. Also 
interesting in one of the devices there appears to be no ballast value, 
that is the curve is effectively flat. Is it also required to match the 
ballast value? What is that resistance called in a MOSFET device? What 
is its purpose?

Thanks, Dan kb0qil