Legacy call sign

[W7PAI]

I will be taking the tech and general test in May, and after I receive my callsign I would like to aquire my fathers callsign of W7PAI. I have searched for this call sign in several databases of available 1x3 call signs, but it never shows up as being available. My father died in 1978, but I can't remember how long he had been inactive as a ham before his death. I have done a google search for W7PAI and the only hit I get is this: http://hamcall.net/call/W7PAI:1960

Can anyone tell me if this callsign is not available?

[K0SPN]

http://callsign.ualr.edu/callsign.shtml shows no result.
The QRZ DB shows no result.
Given those two, I would say that no one is issued that callsign.
You will have to fill out the forms and pay the fee to be issued a vanity call.