Mike, your on in the right church but in the wrong pew.
That series, 3450 3750 etc did come after the 3400-4000 series but they were complety new, different saw's that really shared no parts that I can think of. Don't forget the higher up Poulan Pro version's like the 330, 336, 365 and super 380.
I like the newer versions a little better, as there lighter, slimmer and they just feel right. Plus they have better gear driven adjustable oilers and a better antivibe system.
The downside and not much of one is the A041 style bar mounts they used.
My PP365 is one of my favorites to use.