Sounds like Uncle Bob has already given the road map for this process. Since you're looking to buy as opposed to build it's a matter of figuring out exactly what you want within the limits that you may have relative to room, comfort and accessibility; then once you've narrowed down the type, searching for the right car that fits those needs. The only caution I would offer is that since you're not a "wrench twister" you need to accept that you're buying a one-off, custom car and regardless how it looks it is not going to give you the reliability and factory support you get with a new OEM vehicle. You're going to be relying on a shop to keep the hot rod maintained and working, and shop time is not cheap, which may not be a problem for you. I guess what I'm saying is if you want/need a Beemer 7 Series type comfort, reliability and dealer support you'd be better off shopping for a new Beemer, or even working with one of the old line european OEM's for a custom, one-off ride and support if that's your bag. I'd hate to see you spend $200k for a classy street rod at Barret Jackson, find out it's not what you thought it was, and then find you can only get $80-100k for it when you try to sell six months later after it has some road miles on it.

Good luck on your quest.