For the 1972 Mustang, body side tape stripes were a regular production option (RPO) and only available in conjunction with the Decor Group Option.
If they are not a separate line item on your factory window sticker or invoice, your car was not so equipped.
And all Mach I's did not come with body side tape stripes...
From the 1972 Ford Product Information Car Facts Organizer for Ford Salesmen:
pg C-17 & C-19
"Mustang Options and Accessories
APPEARANCE EQUIPMENT
Decor Group (Includes lower bodyside paint treatment with bright chrome upper moulding, unique black honeycomb grill and sportslamps, color-keyed front bumper, color keyed hood and fender mouldings, plus trim ring/hub caps. (Available on base hardtop and convertible only)."
Note ---- the Mach I's came standard with the similar items from the Decor Group.
Hope this helps.
see a previous post concerning the 1971 Mustang Decor Group RPO:
http://www.7173mustangs.com/thread-d%C3%A9cor-accent-group
Ray