1984 4kq mastercylinder?!

[James Dupree]

Hi all,
I have a deal working on my 1984 4kq and of course something has to happen. The master-cylinder failed! Now here is the kicker it is a 1 year 1 model part. It only fits 84 4kq nothing else. LListprice is $407 and the wholesale cost is about $190!!!!. 
Has anyone put a master-cylinder for a latter 5k on an 84 4kq? (I'm not sure of the part numbers that follow, looked them up this afternoon. The last 3 digits were the only ones that were different between these two parts) I have a 443 611 021 that  is a 23mm master and fits latter 5k (fit a bunch of different cars) the 84 4kq uses a 443 611 019 the is a 22mm master. All the other dimensions look the same but I have not measured or removed the 4kq master to compare them. Anyone BTDT? I don't think that the 1mm diameter change will cause a problem, the pedal should be a little firmer.
And I have already told the prospective buyer so I am not trying to pass off a cheap repair on a buyer. 
Thanks
Jim
1993 S4
1984 4kq (brakeless)
1985 4kq (sold - gone)
1985 5kt (just hanging out)