Three hundred 404s in G Sitemaps.dangerous for rankings?

[Oimachi2]

I installed a classifieds component on one of my sites just for a few days, about 300 categories and 300 dynamic URLs.

I now pulled off the component offline so that pages are gone.

Now I have 300 crawl errors 404 not found with Google but correct 404 headers.

Should I create 300 (301 redirects) or just let the pages fall in oblivion?

Additionally, I have another website with 5000 pages that I want to scrap and start a brand new site but with the same URL. Is it ok to leave all the other pages 404 to be forgoten by Google eventually?

Cheers!

[phranque]

if you have equivalent or replacement content for those pages i would use a 301 for those pages which should be redirected.
otherwise, i would suggest trying a 410 Gone [w3.org] status code response.