USA Side Marker Lights or No?

Looks better without, worth more with.

 

Build it the way you like it-- The welded in rectangles can be cut back out with minimum drama provided the welder knows how to butt-weld with minimal distortion and filler bodywork.

 

Aside from the aspect of originality (not for purpose of increased value, but for its own sake), my opinion is that the recessed marker lights give dimension to the body, and relieve the voluptuousness of the round Dino body shape. That may sound blasphemous to some, but remember that the factory blacked out the rocker panels, first up to the crease line, then half-way up to the door bottoms, to visually lower and lengthen the body section. This may be considered "trickery," but I believe that it is an illustration of Pininfarina's design genius. Fred

 

I can't imagine how a Fiat parts bin sourced rectangular marker light cut into the side of a car that is almost all curves had any Pininfarina input or genius. Those lights are a quicky attempt by Ferrari to make the car legal for the US and are hideous from any angle.

Back to the OP I would say have the car the way YOU like it. As you say it is a keeper so affecting value means nothing and un-doing it is not a big deal should you need or want to sell later on.

 

I welded mine shut and put the euro makers back in.
Much better looking, although mine was a euro spec car, so it's back to original.

 

Yuck - RUINED Italian car design genius on every level, every car they required them on...ESPECIALLY the beautiful Dino. I have to admit I do like the way small round Carello's look on many cars, the euro solution, when on fronts mostly and some rears. It's a car by car thing with me. Same with overriders. I like them on the front of 901 Porsches, and don't like them on many, again car by car.

With Dino, euro spec - front round Carello's, flush front lenses on frunk (front trunk) and covered headlights for my preferred look.