I hate tha fact that most auctions end while I'm at work. The minute I bid on some Ford parts, someone usually will up the ante. One Guy for weeks, kept jacking up the auction price on every F1 part posted on Ebay, he would run them way up and then bail without having to pay the premium price that the final bidder placed. I lost three grills this way!
Waiting to the last moment if someone has bid higher than you is the best tactic, to avoid potential bidding wars.
I also think the car is worth whatever you feel it's worth. If you have a specific budget in mind for the build, stick to it, because it will cost alot more in the end. But if you love this car, as does your son, go for it, the father son builds are the best(worth way more than the money it cost) for the experiences you'll both remember for the rest of your lives! Each and every father son build featured here shows the pride of the Dads and the "cool" factor of the son's for their project. I grew up without a Dad(divorced and uninterested), and wish my Dad had the relationship with me to do such a cool thing! Good for you, and we want to see posts on whatever you guys build!