I believe 74mm is the largest without clearancing.
Check out
European Motorworks
They sell t4 stuff and also do machine work & engine building so I am sure they can balance it for you.
You might also want to check out
Jake Raby
He sells complete engine kits for T4's and they are fully balanced.
__________________
WinterJam 2010: Vdub, Surf, Skate & Musis Fest
WinterJam 2010
'I drive way to fast to worry about cholesterol!'
'67 Sunroof Notchback * '68 FI Squareback