With little knowledge of RF circuits, your attempt to reverse engineer a radio would be futile. Your best bet is to purchase a FM receiver kit. For example:
https://www.electro-tech-online.com/custompdfs/2008/06/fr146E-1.pdf
Even to tweak this kit you will need some RF knowhow to adjust the input circuits and VCO components, but it is possible. Perhaps if you study the circuits, and see if you can come up with values needed to operate at the range you want. I am sure there are peeps here that could assist you once you have studied what needs to be done.
Here is the link for the mixer IC.
https://www.electro-tech-online.com/custompdfs/2008/06/SA602A-1.pdf
I have to ask, why 50 MHz ?