Any ideas for radio install?

[Ozark Ike]

My 71 has a radio delete panel. Somebody cut holes in it to add an aftermarket stereo with speakers on the floor (I promptly ripped that junk out). Does anybody have any ideas on how to support a radio and speaker in the factory cut opening? I don't have the speaker bracket, radio bracket and firewall strap, of course. More importantly, I don't even have the screw/bolt holes in the firewall even if I did buy the brackets and found a radio. So, do you have any ideas on how I can support a radio and speaker in the factory opening?
By the way, why does my truck have an antenna when the old farmer ordered the truck without a radio? Thanks,
Ike