I'm really pissed now!

[82 GT]

Here's the deal:

I saw this ad in the classifieds for a mustang street/strip car that was being part out. I noticed, on the list, was an 8.8 rearend that was spooled, 31 spline axles, 4:10's and C-clips.
I made an offer for $300. He responds back and says "$350 and it's a deal". Fine..I say "ok" thinking that now it's mine.
He emails back the next day and says someone local offered him $400 for it and if I can match that or not.
Knowing that it's still well worth it, I say "ok..I'll go $400 but that's it"
I made several attempts to make arrangements to go pick it up but each time he comes up with an excuse why I can't come.
On Sunday, he writes and says "the rear will be out of the car in a few hours..if you want to come for it then it's ok"
I told him it was too late to go then but asked if Monday would work and he says "yes, that will be ok"
Keep in mind that this is a 3hr. drive for me
I call my buddy who has a truck and tell him it's "on" for Monday and we make arrangements to go early Monday(today) to go get this rear.
Around midnight Sunday, before I went to bed, I check my email, as usual, only to find that this guy with the rear is telling me that "he might have somone that wants to buy the whole chassis with the rearend" and he's going to have to hold off on selling the rear to me.
I hit the f**king roof!!!! I was PISSED OFF big time!!!
Now....I have to call my friend in the middle of the night and tell him that it's off again.
I wrote that guy back telling him he could keep his F**king rear!
I am so glad I checked my email before bed. If I would have drove all that way today only to find he wouldn't sell it.......I don't know what would have happened but I'm sure it wouldn't have been pretty.
Is it just me or what but if you mutually agree on a price for something, shouldn't it be considered SOLD at that point?

If anyone has or knows someone that has an 8.8 rearend for a mustang, let me know.
I have cash waiting and am willing to drive a few hours for one.