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Matt's answer below is spot on. I add that if the site is ranking well for the key pages then I would try and mimic the Title tags and H1's in transition. Why change a good thing. However if the site is not ranking well or can be improved then the transition is the perfect opportunity to review the Title tag and H1. Undertake some keyword analysis and optimize the Title tags and H1's for search today. Always good to review and maybe eliminate some duplication etc. that always creeps in with mine. The meta descriptions in my experience is irrelevant to SEO - only the title tag and H1, out of the 3.  However the meta description does have an impact on CTR which in my view is just as important. So ensure carefully crafted and sending the customer a reason to click through to your website. MattAntonino