My limited experience (and knowledge) there are 3 chassis that need to be kept together.

Lobo.
No link rear, frame and arms are one package deal.

Walsh
CR500 rear, frame and arm are one package deal.

Laeger
CR500 rear, frame and pro-trax front end one package deal.

Once you talk about 450R frames, I am lost. But on 250R frames, that are not stock replacement, you should use the parts that came with it. Maybe you can get stuff to work, but these three are designed as one unit.

Example...
My Axis rear shock was too long (1/2 inch) for my Walsh CR500 rear end. Axis said that the length of the shock was in specs for a Laeger CR500 chassis, not the Walsh. 1/2 inch may not sound like a lot, but caused the linkage to hit the swingarm fully extended.

 

I remember for a long time, Duncan Racing had a Roll no link swingarm for the 250R on their website. It was stated that this swingarm could be used with a stock frame, but there was a rider weight limit. (Dont' remember what it was.) it did require a custom shock though. I just went to the site, and it is no longer listed, but one of the pictures is still there. Under 250R, chassis, and the scroll down to the swingarms, it is the pic of the blue one. It was a gull wing style. Maybe this is what your friend has?

Doug

 

If the frame is a standard Laeger and not the "ProTrax" frame (with T-pin and CR500 rear) then you should be all set.

All three companies made parts for the stock 250R frame (or stock replacement), but they also made parts for just their own chassis. In this day and age, with so many part outs, you might be careful in what you are getting and if it will work together.

I remember some one posting on how they brought a swingarm (laeger maybe) that would not work with their frame.