You 2 must both be younger than me. The 156 172a gasket was added about the time the B series  1800 &amp; the 1600 tractors came along. It was even mentioned in a bulletin. Now good thing I have a simple task to do tonight. I will give it some thought as to why they added it. There is only one not 2 I have not looked at your power steering cylinder breakdown yet. If no answer tonight look Tuesday as I do the school teacher thing tomorrow. If you can find the cover and the pulley that take the lip seal jump on it.