Not much reproduction parts available for this year Road Runner unless it is NOS and those parts are few and far between.

This is what Wikipedia has to say about production numbers.
1975
The 1975 model was based on the newly restyled, more formal-looking B-body which was now called the Fury (the former full-sized Fury being called "Gran Fury"). The Road Runner came with a blacked out grille and a special stripe treatment to distinguish it from the Fury, as well as a heavy duty suspension. As before the 318 was the standard engine, but it was now just with a single exhaust and 145 hp (108 kW). The engine options were extensive; with a two-barrel/single exhaust 170 hp 360, a high performance four barrel/dual exhaust (Code E58) 360 (220 hp (164 kW)), and three 400 cu in offerings; a two-barrel/single exhaust/160 hp, a 185 hp (138 kW) four-barrel/single exhaust, and a high performance four barrel/dual exhausts/moderate cam 235 hp (175 kW) were also available. In Car and Driver magazine testing of a 1975 car with the top line 400 engine; 0-60 happened in 8.1 seconds, the quarter-mile times were solidly in the 16-second range, and the top observed speed was 121 mph (195 km/h). While just a shadow of the 1970 figures, this performance was at least respectable for the times. All engine choices were limited to the 3-speed Torqueflite automatic, with the E58 360 and the 400 engines being available with the 3.21 axle ratio gearing. Plymouth's most powerful engine; the 440, was restricted to police models, though it has been rumored that a few 1975 Road Runners were built (via special factory order) with the 255 hp (190 kW) police spec 440, along with the police spec suspension and wider (7") rims. Only 7,183 Road Runners were built in 1975, and most (just over 50%) had just the 318 engine.
Though the name of the car the Road Runner was based on changed from Belvedere to Satellite to Fury, the Road Runner remained a B-body through 1975. While the Road Runner name was planned to be on a B-body in Plymouth's published literature for the 1976 model year, the name was transferred to an optional appearance package for the all-new Volare.
1976–1980: F-body Trim Package