Anyone ever have or ride one of those old yamaha RD 350's or 400's?  They look like a fun bike.  I have heard that on the 350 it was easier to pull the front wheel up (then on the 400) is this true, what it just the weight distribution?

Whoever told you that is full of it.
The RD350 was underpowered and it handeled like there was a gate hinge in the middle of the frame. The RD400 had more power and better brakes, it also handeled like it had a gate hinge in the middle of the frame.
The last year of the RD400 (in the USA) was the best of the series. It was the RD400 Daytona Special. It had better suspension, wheels, brakes and engine. It could never be called a "great" handeling motorcycle though.
I owned an RD400 and a Daytona Special. Both of those bikes would wheelie with no problems in first and second gear.
Unless you are buying it real cheap or you have money, time, tools, and are mechanicly inclined, I would not buy one for transportation.