I have a KSB1B and getting the flange & downpipe at the turbo end was no day at the beach.
I don't know about the 40, but the KSB1B was 1" longer longitudionally from centerline longitudionally of the exhaust manifold to the end of the turbo which made getting the mate to the downpipe a challange.
I finally got it right, but took several tries ($$$) of the flange and downpipe welding to get it right. There might be a better mate system now.
My KSB1B I got for towing. Low end spool is a little slow, but I got it for towing and I am sure they can be setup for just about any application.
There is a thread that has pics of the 40 and B1 shafts and wheels side by side. The B1 is much beefier, but also therefore heavier ... ... .
Bob Weis
For what I want it to do it works VERY WELL for me!