Several choices. '65-'66 front disc masters are only single stage fishbowls 
'67-up are dual stage
If you've retrofitted, then you'll be into new lines from m/c to p/valve and j/block anyway, so I'd go with a later model tandem.I put a tandem m/c out of an '83 Ranger in my '65 GT (front discs)... plumbing is on the correct (driver's) side, pushrod length is the same (not the case with '67 units, requires an adjustable rod), it's aluminum, looks cool 
Once again, the only trick is making your own lines unless you buy all repop '65-66 stuff 
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1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9"
All Blue Oval, no blue bottle
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