If you're talking more about "specialist's varieties" (like R5-R7 varieties that are not listed in the Redbook), auction records are going to be the only source to determine an accurate value. Although priceguides can supply you with accurate values on major varieties like overdates, when it comes to the more specialist varieties, priceguides will do you no good.
I'm looking for the price guide on the major varieties, just so I can familiarize myself with the varieties and have an idea of their values.
PCGS CoinFacts provides values on the major varieties, which they base off of auction records. Still, your best bet would be to search some of the auction house's online archives to determine the most accurate value. PCGS CoinFacts is not always 100% up-to-date with what coins have sold for at auction in the recent past. I highly recommend searching Stacks-Bower's archives. It's easy to navigate, and they sell major CBH varieties regularly.
Yes, there is a published guide and it is excellent. Buy Stephen Herrman's AMBPR (Auction and Mail Bid Prices Realized) for Bust half dollars. It covers FH, DB, CBH and RE half dollars for R3 and rarer die marriages and popular die marriages. It contains historical price, grade and sales data going back for 5 years on the most common coins through as far as the data can be found for more rare pieces. It is published quarterly, if I recall correctly, and will cost $30 or $40. Buy it!
Thats exactly what I'm looking for, I've searched for a bit and cant find a place to buy it. Have any ideas? Thank you