Tractor Repair: Hydraulic lift on 1976 444 international gas tractor, northern hydraulics, head bolts

Question
Have a 1976 International gasoline 42 hp C153 engine tracto.
Retired industrial engine  mechanic/maintenance---
The front bottom of the self contained hydraulic lift leaks oil when the lever is activated.
The oil leak comes from the front control mechanism that house the controls and piston.  It is made in two pieces-- put it together about 5 years ago and worked fine.. tightened the 3/4 head bolts to no avail.
Question-- is there a gasket that goes between these iron plates?

when I put it together there was none in there-- Tightened it in sequence like a head-  no leaks--
If no gasket goes there - what type of sealant can I use--
I bought a pressure limiting bypass unit from Northern Hydraulics to limit the oil coming out-- It works- but diminished pressure limits the load I can pick up-- the limiter is on the outside and adjustable with an Allen wrench.

Answer
Hello,

  I'm not 100% sure which part is leaking.  You can see a breakdown of the parts you are looking for by going to caseih.com and selecting parts and services, then click on search for parts.  Type your model in the search box and click search, then select your model from the results.  Go to the hydraulic section and you will be able to see exploded views of the parts with all the part numbers.  You will be able to determine if there is a gasket or o-rings or whatever you need.