Tubes ware out so keeping the old tubes just for the fact they are old/original can actually be dangerous, you wouldn't want old tyres on your car would you?

Any amp that age will need the electrolytic capacitors renewed, the two prong power cord replaced to a three prong cord and the death capacitor should be disconnected.

I understand wanting to keep an amp as original as possible but it also needs to be made safe which is much more important if you plan to play it.