There is not a built in luggage mount in the engine lid as in an original car. If you are not going to put much weight on it, I guess you could drill some holes in the opening on the lid (in the correct places of course). You would probably want to put some body washers under the mounts and nuts to spread the load.
I would think mounting on an Intermeccanica is the same as any of the other cars, grill differences perhaps creating the only issues.
$350 is not bad for a Leitz or a good repop. NLA Porsche parts in Reno, NV sells a repop of Leitz and Reutter racks, and the hardware to mount them on an original car. Vintage Speedsters also makes a version of a luggage rack.
www.nlaparts.com/catalog/index.php?cPath=221&osCsid=d3e5e6d6a4d77fad376d0affdd91b9a7