A forum search didn't find anything recent. I'm looking for a 64 - 66 401 or 425 nailhead and an ST400 transmission for a future project, but I don't have any gauge of fair market value. I want to get a fair shake and also not offend a seller with a low-ball offer to where I lose an opportunity. I've located a complete (oil pan to intake, water pump to flexplate) 425 and ST400 w/converter combo out of a 1966 Riviera and will be meeting the owner soon to look at them and hopefully make a deal. It's a "best offer" deal, and we haven't discussed price. The owner knows nothing about the engine and transmission aside from that they turn over by hand and came out of his project car. He's unwilling to pull the oil pan or valve covers, so the best I'll be able to do is turn it over and peer through the intake runners, distributor hole, and breather holes. The speedo is missing from the car, so no estimated guess on the mileage. The chassis is already restored, so no guess on the mileage there either. From the photos, the engine and transmission are dressed stock with typical aged paint, dust, oil buildup but nothing that would suggest they are greasy unmaintained junkers. Questions for those in the know, preferably on Rocky Mountain region pricing: What is an unknown-condition complete 425 nailhead worth? What is an unknown-condition complete 401 nailhead worth? What is an unknown-condition complete ST400 w/converter worth? Thanks for the help.