I investigated this a little when I knew I'd be replacing the 270 in my '57 GMC 2 ton,but ended up going a different route.
I think a V-8 side-mount conversion "tube" type crossmember might work with a little modifying. Near as I can recall,the stagger from one side to the other on a 292 is about the width of a V-8 motor mount,so if you make a couple of plates to weld on and offset one about half a motor mount width forward of center on the left and offset the other one the same amount to the rear on the right side,and drill the motor mount holes to match the new "stagger",it should be a relatively close match. This is just my opinion,above all else,measure everything,re-measure,double check and measure it again,and keep checking your measurements. It's a lot easier to fix a mistake when it's still just one than it is to have to fix a bunch of mistakes that were all based on a mistake made early on. There's probably quite a difference in frame width from your '40 to my '57,but I'm sure someone can fill you in on that.
When I put the 292 in my '57 GMC dump truck we made a saddle mount that bolts to the front facing of the engine. That enabled me to use all the stock '57 mount cushions,etc. ,it left clearance for the exhaust and other stuff that was otherwise in the way and all the clutch linkage lined up like original. The mount turned out pretty homely,but works great.
Speed
