I suggest getting a tech to check the amp for AC leakage from the electrolytics before replacing them if they're still testing fine and have no signs of bulging or leaking electrolyte i'd keep them in and reform them, aslong as they're not putting a ripple onto the filtering they're usually good to go, Im not for re-capping an amp because it surely changes the tone the old RS/Erie and LCR caps are much better than the stuff on the market now, I do agree with JPF, F&T make a fine cap and I use these in my own builds.
There are mixed opinions on this subject though, so I if your want 100% reliability simply just replace them all as a cap blowing in the HT line can cause all sorts of problems that weren't there before, you need to be sure these caps will last if you keep them in and a visual inspection alone isn't really enough.
If you're not sure about draining the smoothing caps i'd get a tech to do the work for you.
re changing electrolytic caps. I can see the attraction of the "if it ain't broke don't fix it" approach, which is also the cheaper option.
However, I've also seen plenty of amps from that era where an electrolytic cap failure has caused damage to other components (ie an expensive repair), so I'm not convinced that leaving components with a limited lifespan until they fail is a sound approach either.
I've seen no evidence to suggest that old Erie/LCR caps are better than good quality modern electrolytics.
Notwithstanding the fact that it is impossible to compare like with like here (ie you are comparing a 20-30 years old part which ages with a new component), the only aspect of older caps which I have measured that is better than new caps is that old caps are more tolerate of over voltage (measured by destructive testing). This isn't because old caps are better, but simply that tolerances on old electrolytic caps was so bad, often +100%, -50%, that a significant margin for error had to be used to ensure correct voltage compliance.
