Hum, I think you're getting muddled there - the LC 475 is very different to the LC III. The LC and LC II were very similar to each other, but the LC 475 has more in common with the Quadra 610, 650 and 800. Even then the chipset isn't that similar... just related.
The LC III has much lower (what is it, 36MB by default?) RAM limits, but there are some hardware modifications that can get you higher than that, but not easily, and not 136MB.