I agree with Rrog, The amp is a classic and I wouldn't change anything on it. I would have the caps checked because they can leak when they get old. You said that it is currently down. Instead of spending money to modify it. I would consider sending it to Audio Research to have it fixed. They will go over everything and bring it back to the original specs. Put a set of new tubes reputable dealer in it first. That way ARC will not have to replace tubes. I sent my V70 in a while back and I was amazed at how good it sounded when it came back.
To replace the captive power cord with a IEC socket might be difficult. There in probably not enough clearance between the case and the board.
There are some speaker cables with smaller spades or you can replace the spades with smaller ones. As I mentioned I used and still do use Audio Research speaker cables. They are really nice cables and can be picked up used for not a lot of money. The spades will fit between the dividers on the strip.