How can I redirect this contact form to a specific permalink

If your form has been incorporated into WordPress as a page template, which I encourage, then get_permalink(8); // or 12 should do it.

If not, then http://example.com/?p=8 and http://example.com/?p=12 should always work. http://example.com/?page_id=8 and http://example.com/?page_id=12 uses the proper parameter for pages but ?p= works fine when I test it.