1999 KX 250 / 125 frame difference

I was wondering if anybody knows what the differences are in the 1999 KX 250 and 125 chassis. I know the rear rims are different sizes and the swingarm might be longer. But was wondering if there was a big frame difference. I am in the process of putting a KDx 200 motor in my 250 chassis. I would appreciate any info.
Thanks
97 moto
:laugh: