I Have given this a lot of thought.
(the conditions in my opinion are that money is no object, you have unlimited space, and you can have as many things as you want.)
In order of the films he made:
THX1138:
One of the full Guard costumes
American Graffiti:
the Yellow hot rod with the "THX 138" plates
Star Wars: Episode IV: A New Hope:
the Tantive IV
The Model Escape Pod
A Full Sand Trooper suit
Rebel Trooper Suit
Death Star Gunner suit
Luke's T-16 model
R2-D2
C-3PO
Red Leader Rebel Pilot Costume
Original Luke Hero Red 5 helmet
Model of Vader's modified Tie Advanced X1
One of the short and tall Laser cannon turrets
E-11 blaster with fully working stock
Han and Luke's heavy blaster pistols
A Hero Storm trooper helmet
a Full TIE fighter pilot suit
"Ben" Obi Wan Kenobi's Lightsaber
Original Jawa costume
Sand Crawler Model
Kryat Dragon Skeleton
Star Wars: Episode V: The Empire Strikes Back:
The Imperial Probe Droid
Full Chewbacca suit with all his props
A full Suit of Snow Trooper armor
John Ratzenberger's Rebel "Major Derlin" costume
AT-AT Animatronic model
Boba Fett Full armor
Vader's Full armor
AT-AT Pilot and driver costumes
Cloud City Cloud car
Platform 38 model
Han in Carbonite
Vader's light saber
Slave I model
5 ft Falcon
Large Super Star Destroyer
Rebel Fleet's Medical Friggiate
Luke's Bacta container
Yoda Puppet
Snow Speeder
Indiana Jones: Raiders of the Lost Ark:
all the Whips
Indy's Revolver
Indy's Hat and jacket
The Ark
Star Wars: Episode VI: The Return of the Jedi:
(NOT SAYING the SLAVE LEAH METAL BIKINI because I Have Seen WAAAAYYY to many of those at Halloween parties/conventions, and Know how to make them)
Shuttle Tyderium
Death Star 2
Emperor's chair
The Rancor
Scout Trooper full armor
Speeder Bike
B-Wing model
A-wing model
Y-Wing model
AT-ST "Chicken Walker" model
Ewok Costume
Imperial Red Guard costume with Force Pike
Captain EO:
The little robot helper
Indiana Jones and the Temple of Doom:
The Machete that Indy uses
The "Club Obi Wan" sign
Labyrinth:
Hoggle puppet
the old man with the bird hat puppet
Tucker: The Man and His Dream:
one of the 50 Tucker cars
Tucker's armored car
Indiana Jones and the Last Crusade:
the Tank
Henry Jones Sr.'s hat, bag, and umbrella
the "Mortar" (FX) and motorcycle that flipped with the costume on the original dummy that they had it on
Henry Jones Sr.'s Grail Diary
The Jones Motorcycle and Sidecar.
The old Knights Armor and the Holy Grail
Star Wars: Episode I: The Phantom Menace:
Qui Gon Jinns's Light Saber
Darth Maul's Sith Probe Droid and Speeder Bike
Anaikin's Podracer (Trivia: The engines are modified versions of the same jet engine used in the Vietnam era F-4 Phantom II's)
Maul's Stunt saber
Naboo N-1 Starfighter model
Anakin's Pod racing helmet
Yaddle Puppet
Battle droid
Naboo Pilot helmet and goggles
Droiddeka (destroyer droid)
Naboo heavy grip Blaster pistol Padme's throne with compartment with Short barrel "Hold out" blasters
Padme's Long barrel blaster
Padme's Royal wardrobe
Battle Droid Blaster
Qui Gon jinn and Obi Wan Kenobi's A99 Aqua Breathers
The Full size "Damaged" Otoh Gunga Gungan Sub from the Deleted Waterfall scene
Naboo Queen's Royal Starship J-type Nubian 327, class 1.8 Hyperdrive core
MTT model
AAT model
Trade Federation Droid Starfighter "Vulture Droid"
Star Wars: Episode II: Attack of the Clones:
Padme's Naboo Starfighter Pilot Disguise
Senator Padme's Wardrobe
Zam's Blaster rifle
Zam's Speeder
Anakin's "borrowed" speeder
Jango Fett's Kamnio Saber Dart
Jango Fett's Stunt Armor
Jango's "Arena" Jetpack
Jango's Hero Armor with standard Jetpack
Model of Obi Wan's Jedi Starfighter
Anakin's V1 Cyborg Hand
Yoda's Lightsaber
Mace Windu's BAD ***** Lightsaber
Model Hailfire Droid
Super Battle Droid
Count Doku's Lightsaber
Phase 1 Clone Trooper armor
Phase 1 Clone Pilot armor
Star Wars: Episode III: Revenge of the Sith:
Anakin's V2 Cybernetic arm
General Grevious' Blaster
Senator Padme's Wardrobe
All Wookie Props
All Wookie costumes with armor
Supreme Chancellor Palpitine's Lightsaber
Medical capsule
Padme's box of treasures
Red Tails:
P-51 B/C Mustang Model