Actually, I'm not trying to save money...at least in the short-term. I've chosen this route knowing it would be more expensive than simply finding an old MTB.

I want a bike that has specific characteristics that are not normally found on MTB's. I want shorter chainstays, a shorter top tube, a lower bottom bracket and a lower amount of trail. I love the agility of 26" wheels and I love really fat, smooth tires. I can get some of these characteristics in a hybrid and some in an MTB but I've never seen a bike that has all of these characteristics. So, while the recommendation to buy an old MTB is, generally speaking, a good one, it's not what I'm looking for. Think of a bike that is somewhere between a Bridgestone XO-1 and a Rivendell Atlantis.

I have communicated with a custom frameset builder and my general BikeCAD idea (not the 730 conversion I posted here) is very close to a bike he already builds. My design is based on my experience riding bikes and knowing the geometry of those bikes and figuring out what I like and what I dislike. When the time comes to commission him to build a frameset he will actually design it but I want a general template to give him that I can say "I've been riding a bike with these characteristics and I really like it". This will give him a very specific idea of what kind of ride I'm looking for. My 730 with 26" wheels is very close in geometry to the custom idea I've been working on. I don't mind spending a couple of hundred bucks on this experiment if it helps me nail down exactly what I want on a $2000 custom frameset.