73 thru 77 are basically steel Rally wheels fitted with GR70-15 tyres.
However in 73 a cast alloy wheel was available but was " hecco en mexio" - and because of flaws was discontinued.
The tyre coding changed and your car would from factory most likey have steel rally wheels now fitted with P255/70-15 Goodyears.
I believe you could option for 60% profile tyres, and white lines &/or lettering.
From 78 onward Rally wheels were std, but the Alloys returned after the casting flaws were fixed, and were options 78 ~ 82.
My 78 has 15" Rallies and 255's all round, but is a stock setup. Ergo there are no issues with 60 or 70% profile tyres, they clear, drive and handle as good as any 78 car can do.
That's actually a lie, the 78 has 255' rear and 225 (ex "Stingray's) on the front, don't ask its a long story, but that combination makes the car look like its ducking down in the front to get under the limbo stick.
I know a person, who has a set of Rallies with 255's fitted !?. In fact there may be a set of S/S trim rings & caps. The tyres are Waaay tooo old and RS, but for static display, they'd fill the bill.