If you move from Blog*Spot to WordPress, you’ll likely have many inbound links still pointing at your Blog*Spot site. There’s no reason to take down your Blog*Spot site and lose the traffic those links generate. However, you also want users to find your new site.
If you want to redirect users from a specific post on your Blog*Spot site to that same post on your new site, look for this section of your Blogger template:
<$BlogItemBody$>
And add something like this right below it:
You are viewing my old site. You can my new site.
This will take users to a search results page, which, if you use fairly unique post titles, will lead the user to the correct post.
WebbleYou specializes in helping you move from Blogger to WordPress. Please contact us if you are interested in our services.