Which would you recommend? sand blasting or blocking? The reason behind your recommendation would be greatly appreciated

The reason for your question is needed before an answer is given. What are you sanding? Body panels are one thing, frames and other parts are something else.
Not trying to put you off or be a smart alec, but I suggest you use oue SEARCH feature located at the top RH corner. Use words 'sanding' 'preparation' 'blocking' and 'block sanding'. You can read A LOT of useful information by doing so.

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MY 69 (http://www.chevelles.com/cgi-bin/xchange/xchange.cgi?search_and_display_db_button=on&db_id=22&exact_match=on&photo_size=full)
My 65 (http://www.chevelles.com/showroom/JPs65frt.jpg)