I have done this many times on many engines.
What I do is lower the crank by loosening all crank bearing caps about 1/2", .
This puts a bind on the front seal but if it's in good shape it will survive.
The crank should drop about 1/8 - 3/16 in and provide ample room to slide upper seal half in place.
Do not totally remove the remaining crank caps.
Use a small jack to gently reposition crank and seat seal, make sure all bearing inserts are in place and finish by torquing all caps per manual. (I know nothing about Oliver 70's maybe they have babett bearings).
Good luck there are several kits available that uses a pin in the oil galley to push the bearing but I don't really think they will work with cork.