Brad that series topped out at the 4000. The 4200 started another chassis design. You will catch on quick, there no real mystery to them.
I have some IPLs and Service manuals for that series if you need them.
I was just over at Acres checking them out. Yeah, it looks like the 3400-4000 were the same saw and th 4200 was quite a bit larger. Looks like the 4000 is 65cc.