My B3200 is a 4 cylinder ... not sure I would call it an economy model. Now the B3300SU is basically the same tractor but no mid PTO and 1 hp more and is considered an "economy" model ... at least according to my dealer.
B, L, & M designate to some degree frame size and rear drive differences. The L has a much heavier rear end than my B.
I was mainly refering to the L series. Because currently the 00 IS economy, and the 40 is Grand.
They dont have "grand" tractors in the L and M.
And like I said, I dont know a whole ton about the older ones. It seems that they started the GrandL's with the 00 designation, like the L2900 and L3600.
When they updated them to the 10 series, I beilieve from then on, the 00's were economy. And then they updated the grands to a 30 and now a 40.
But the grands just have more features for their given year. I dont know about the past, but things that are currently different between the GL's and economy L's are things like Mid PTO option, Open station, push button this-and-that, digital dash/cluster, etc.
I imagine that in 10 or 20 years, the features that make the Grands Grand will be standard on the economy tractors, and there will be newer and better things that will set the grands appart.