D - 52Carl isn't wrong when he says it would be probably "...much simpler..." to go with a 235 or 261. However, if you really want to pursue installing the 250, you might get some inspiration from fellow Bolter Joe H's
250 powered 1937 Chevy Pickup. His Gallery Page is probably pretty dated as I think he's done some further changes since it was posted, but it's food for thought for you.
I would suggest you search Stovebolt using this
LINK to see what older posts you can find that discuss installing a 250 in the earlier truck chassis like your '40.
You may find that if you follow Joe's path, your conversation may need to move over to the
HiPo Shop to take advantage of all the discussions and details involved with changing out more than just your engine.
