I am considering the purchase of a M20F with an extensive list of 201 modifications including 201 panel, cowl, windshield, windows, wingtips, root fairings among others. I have been supplied copies of the 337 forms. Unfortunately the mods were done on or before 1990 when the requirements for the 337 forms were not as strict. The 337's are pretty vague on how these modifications were installed and most have no reference to any STC or existing installation. I am concerned that I may have issues properly insuring this airplane with these issues in mind. I am also concerned, although to a lesser degree, that an IA may find basis to refuse inspection on the basis of the aircraft being operated outside of its type certificate because of these "in the grey" 337's. The plane has complete logs, no damage history, and is in compliance with all applicable AD's. Most of these mods were done by "the mod squad" with address in Missouri, I am not sure if its the same Mod Squad that is now in business exclusively in Florida.
Does anyone have any thoughts on how best to go about finding some reassurance?