I couldn't agree more with the comments already posted. I too love the clean sensuous lines without flared fenders or spoilers. But, I also love the muscular appearance of a flared car WITHOUT the "wannabe" Countach wing!
It will be YOUR car, so get what you want! But please, DO NOT BUTCHER A NICE ORIGINAL CAR TO MAKE A GT5 CONE!!!
As for values, you can search current and sold listings on Ebay and BAT for starters, as well as check out other sites with cars for sale (Hemmings) to see what people are asking. Avoid aggregator sites like Trovit or any other site that doesn't list the seller's contact info, but instead wants you to complete a form with all your information to inquire; such sites merely scrape the web for other people's ads and show them as their own, often presenting unrealistically low prices from early auction bids.
Ebay current auctions/ads:
Ebay Sold listings - not sure how to extend the range of sale dates
Bring a Trailer (BAT)