At first glance, it seems like there shouldn’t be a difference.
When you plug an iPod into a head unit, one of two things happens.
In some cases, it’s even more complicated than that.

Pixabay
So What About iPod Car Adapters?
The easiest way is to install a power amp with RCA inputs.
Then, use a 3.5mm TRS to RCA cable to connect your iPod or phone to the amp.
Otherwise, you’ll probably have better luck picking up a cheap head unit that has an auxiliary input.