Need some help with rf transformer design

[_rushin_or_draggin_]

Hey all,
I am currently in the process of designing a very, very small scale rf amplifier to better understand how they work. My plan is to use the IRF510 MOSFET (not really an RF mosfet but readily available and used in the ham radio community a fair bit) in a common source push/pull topography to amplify a 4W signal to about 50 or so watts for the 20 meter band. Again, nothing really crazy, just to prove the concept. Anyway, I am kinda stuck on how to design the input and output transformers.
From simulation (and comparing to a few other very similar designs) I see that my input transformer should be close enough to a 1:1 for 50 ohms (I have seen others use bias tees to test input impedance but I would appreciate hearing other methods), but I can't decide on how to go about making it. I'll admit, I do not have much experience at all with making transformers. One issue I'm facing is multiple types of cores of the same material. For example, when looking at fair-rite's line of ferrites, such as mat 43 or 61, they have quite a few choices of say Mat 43, but they all have difference impedances and response curves shown in the datasheet. My question is what exactly do you look for in these cores.
Is there a recommended method to choosing a few to order and then once they arrive another method of testing them for your design? I attached a datasheet for one of the cores in hopes someone could better explain what exactly I am looking at.
Thanks in advance!

[Solder_Junkie]

There is a good design using those transistors here:
https://www.qrp-labs.com/linear.html

There is a pdf construction manual with transformer core and winding details. I think you expect too much in terms of power, 10W is more reliable.

73 SJ