What provisions in the regs (or FSDO policy) are there for recertifying an airplane that was previously built by re-building it and claiming yourself as "builder"?

If you prepared a "dissassembly log" as well as an assembly log has it been proven that you performed 51% of the work necessary to return a previously un-airworthy aircraft (perhaps even surrendering the Airworthiness Certificate) to airworthy status. Does engine assembly count towards the 51%?

I would like to find a Kitfox that I could re-build only if by rebuilding it I could obtain Repairman Certificate privileges.

Has anyone run into problems finding an A&P willing to perform maintenance/inspections on a Kitfox?