I'll put my vote in with Paul... chances are kinda slim that you'll find a good existing driveshaft with ends that match your old & new hardware, in exactly the right length.
Get the tail-shaft yoke that goes with the transmission and your original driveshaft, then take them to a driveshaft shop. They'll likely want to know the length you need between the centers of the front & rear u-joints. Allow for the trans yoke to be centered in it's front/rear travel when the truck is at normal ride height.
If you have questions they can tell you how to get the measurement they need. I'll suggest having the trans installed first (in case something needs to be modified to get it to fit) so the length is 99.9% confirmed before they build it.
You'll get back a straight & balanced driveshaft that is already finished with new joints, and it will probably have some sort of warranty too.
(and you won't have to watch for snakes)
.