[Amps] Variac Question

[Larry]

I am building an amp and have started gathering parts for it.  My plate 
transformer secondary is rated at 3500 VAC.  Thats a little much for 
what I need.  I need to end up with about 3500 VDC for the amp.  I found 
an old General Radio Variac type V10 good for 10 amps, but I'm not clear 
if it can be used on 220 VAC.  The wiring diagram on it says "volts 
shown for input 115 volts 50-60 cps."

My question is Can I put 220 volts across the coil without smoking it?  
I'm thinking that it would work.

My other possibility is a pair of 110V 5 amp variacs that I have that 
are ganged on a common shaft.  I'm thinking I could series wire the 
coils and apply 220 V.  The problem then is that they are only rated at 
5 amps each, which is not enough for a full power amp.

Anyone got any ideas short of going out and buying another variac?

Larry W4LK