Jcd has it right in my opinion.
What I've done in the past (with similar storage options) is to spray the day-lights out of everything with a rust preventative (I like LPS 2, or if you don't mind the mess LPS 3) then I cover the entire assembly with a plastic bag/s.
Thsi has worked for me, my $0.02
1995 E320 40K
1999 Tahoe 90K
2002 JX8 Sport 43K
2005 Volvo s40 65K