[Harp-L] Original 64 Fender Deluxe blackface amp questions

[nonidesign@xxxxxxx]

I have an original 1964 Fender Deluxe blackface amp that I want to use for gigging. . I'm going to do the usual stuff such as replacing the 2 prong plug with a grounded one, recap if necessary, etc. 

Anyone have recommendations for:
1.  a replacement 12" speaker (ceramic, alnico, brands, vintage, new, etc.)?

2. harp set-ups good for this particular amp (tube set-ups, how the amp behaves with certain mics, control knob & input preferences, etc.)?

3. The amp has an external speaker jack. I seem to remember a rule for external speakers such as using one at half the ohm load for the amp's main speaker ( I beleive the stock speaker is 8ohm). Does anyone have any info on this? I don't want to plug in an extension speaker that will cause havoc with the amp. 

Thanks in advance