Are you experienced?
If not I'd suggest a 5F1 kit build first.
Educate yourself and be aware that the safety warnings are no joke!
If you have some experience then I'll give advice for what it's worth (free).
Radios in general are not good donors for guitar amps.
Many you will find will be field coil variety leaving you to purchase an output transformer and the related
circuit changes to make that part work.
The preamp/output stages are extremely minimal value on radios also.
Nearly every tube you'll find in them are dedicated to...radio stuff.
Old car radios are actually better if you are going that route, often a 12AX7 and 6V6's in those.
With that info the best bang for the restoring buck is old PA amps or discarded organ amps.
Do not tear up good organs though!
I've seen organs still going from free to 100 dollars that might be loaded with 12AX, 12AU and AT7's...a couple
of working amps inside (frequently separate tone and reverb amps).
I've made Spitfires from just the reverb side of some Baldwin organs for example, only things to buy were a suitable
power transformer and a blank chassis.
Take a look around this site, in this area.
You'll see some of the work done, great lessons in here.