Think twice about choosing a place that sells cars to perform a pre-purchase inspection. They typically don't have the domain expertise to evaluate your specific car, (neither do most appraisers for that matter) and a place that sells cars has a conflict of interest built right in.
When I've called on national inspection services to look at vintage or special interest cars, I've had "inspectors" who are used to looking at lease return vehicles.
Your best bet is club member who has points judging credit or one of these guys:
http://www.i-van.org/ most of them are appraisers, but cannot own or have interest in a business that sells or restors cars, to maintain objectivity and impartiality. They are also all car show judges with one national club or another, mostly AACA.
Hope that helps!
~Patrick