When you fit the rack the uprights need cutouts in the stock chrome mudguard side panels. (#6 and #7 in image below). From memory they come with the kit but can be purchased separately.
http://
www.ajsmotorcycles.com.au/partFinder/fiche/triumph/0/rocket-iii-classic-roadster/short-passenger-backrest-luggage-rack#A9738071e
# On Diagram Part # Description Price Per Item
1 A9738071 T1 PASSENGER BACKREST x1 $535.75
2 A9733501 T1 PASSENGER BACKREST x1 $96.70
3 A9733502 T1 LUGGAGE RACK x1 $88.35
4 A9750265 T1 PRESSING SUPPORT LH x1 $66.95
5 A9750266 T1 PRESSING SUPPORT RH x1 $66.95
6 A9750282 T1 MUDGUARD COVER REAR x1 $96.65
7 A9750283 T1 MUDGUARD COVER REAR x1 $96.65
9 A9910052 T1 SCREW DOMEHEAD M6 x4 $1.45
10 T3205254 T3 BOLT,HHF,LGHTD,M8X1. x4 $1.80
11 T3350004 T3 LOCKNUT FLANGED M8 x4 $2.75
12 A9910835 T1 BOLT M8 X 1.25 X 35 x4 $2.85
13 T3350700 T3 NUT FLANGED DOMED x4 $2.45
14 A9710032 **Loop ->T2080296 x2 $1.35
15 A9710033 T1 EDGE TRIM SHORT x2 $0.30
Reference: 1
T1 PASSENGER BACKREST
A9738071
$535.75
And the passenger back pads were/are extra !



AJ's Motorcycles - ROCKET III, CLASSIC & ROADSTER 0 - Passenger Backrest Back Rest
Ref Part # Description # On Diagram Price Per Item
1 A9708177 T1 PASSENGER BACKREST B x1 $178.60