After serious thinking George Fields wrote :
Quite a few decades ago I decided a pickup needed a new motor, so
I bought a rebuilt motor from Sears. I never got around to sending the
old motor back for a rebate, and it's been sitting in my garage since
then, in the crate.

I was thinking of taking it to a local auto salvage and seeing what they
will give me for it. I guess it's not a very popular engine anymore, but
I thought I would ask you what you think it's worth, so when I go there
I can know if I'm getting a good price.

What do you think the motor would be worth?

What was the problem with the mouse motor you replaced? That engine is
still very popular and can be fun to rebuild as long as the block is
sound. The heads are replacable and are very inexpensive. I still have
a 350 mouse block on an engine stand sitting in the corner of My home
garage. I plan on rebuilding it and using aluminum heads to replace the
iron heads it came with.
Keep that mouse motor and rebuild it! You'll be surprised at how fast
it will be snached up!