Like I mentioned on PBN, it's not about the gun or the cost. It's the building that makes it special. If you REALLY want to make a spimmy and it takes you 5 years, then so be it. In the end, it's all yours and not someone elses junk you just happened to buy, just to strip the parts off and bolt onto a spyder body.
However, if you need a gun desperately and soon, then I'd go with a Timmy.
Edit - do you really spend that much time thinking about your belly button?
second edit - someone's going to wonder what the heck I'm talking about....