Hi Max,
        I just did this same fix on my '91 and it was very tight. I replaced all
the rubber hoses as well as the cross piece so I lowered the tank partially
to gain access to all the hose connectors. It definitely took more than a
half hour. My crosspiece was also clamped onto the body of the van. I
attached all the new 5mm black rubber hoses to the tank connections and on
the crosspiece at each end. I lubricated the nylon Y connector ends that go
into the tank top with a little silicone grease, this enabled them to slip
right into the grommets without any difficulty. I then placed the
crosspiece in its clamp and tightened it up so it was hanging in place
ready for the tank to raise up to it. I put the new tank grommets in the
top of the tank first before raising it. I scraped up my arms pretty good
reaching over to the top of the tank and popping the crosspiece into its
grommets. I think next time that I will remove the 2 expansion tanks from
each wheel well to increase the accessibility to the tank top.  Try getting
those 2 things out of the way. Hope this helps.

Rick Koller
'90 syncro westie
'91 gl and carat