In case it helps, I also dug out this pic of my old Sammio with custom made lowered floorpans
I would say from personal experience that for you as a first time builder (as I was when I did my Sammio) any of this 'type' of kit you will be fine with, so just choose the one you most like the look of
Each has their own challenges. On the Sammio you can keep the donor bulkhead in place and leave the steering and gear linkage alone, which I would of been nervous tackling on a first build. But you have other challenges such as the bonnet mounting and hinges to deal with and now that I'm just about done with the initial build of my Miglia I'm happy that there are simple and robust solutions to the quirks of the Miglia.
I'd suggest you start a build thread and not worry about making mistakes as we've all made them and laugh about the, and at the end of the day these cars are so simple that just about everything can be redone with a cutting disc, a bit of fibreglass or a welder