In 1970, the 914-6 did not come with sway bars at all. They were only available on the GT, and they were sized differently than a 914-4.
The sway bars became available on the 914-6 in 1971, and they were different from the 914-4 bars. They used the same mounting and connectivity, but they were different sizes.
No 914 was ever delivered from the factory with only a front bar.
@dr914 @autoatlanta.com .. you want to chime in here? I think you have the part numbers for the 914-6 sway bars.
Clay