Your content goes here.

The most important structural decision

I would not make "Sunbeam" the category.

Everything on the site already is Sunbeam.

Instead, I'd make the model the fundamental content object.

For example:

SUNBEAM CARS
│
├── SUNBEAM ALPINE
│   ├── History
│   ├── Series
│   ├── Specifications
│   ├── Identification
│   ├── Production
│   ├── Technical
│   ├── Restoration
│   ├── Parts
│   └── Gallery
│
├── SUNBEAM TIGER
│   ├── History
│   ├── Series
│   ├── Specifications
│   ├── Identification
│   ├── Production
│   ├── Technical
│   ├── Restoration
│   ├── Parts
│   └── Gallery
│
├── SUNBEAM RAPIER
│   ├── History
│   ├── Specifications
│   ├── Identification
│   ├── Technical
│   └── etc.
│
└── SUNBEAM STILETTO
    ├── History
    ├── Specifications
    ├── Identification
    ├── Technical
    └── etc.

That creates a consistent template for every significant Sunbeam.

And this is where your Divi 5 work could become really useful.

You could eventually create a Sunbeam Model template and populate it with different model information rather than manually designing every page.

I'd also create a "Sunbeam Encyclopedia"

This is probably the piece I would be most excited about.

Imagine:

SUNBEAM ENCYCLOPEDIA

People

• Louis Coatalen
• Norman Garrad
• etc.

Models

• Alpine
• Tiger
• Rapier
• Talbot
• Stiletto
• Hunter

Companies

• Sunbeam Motor Car Company
• Talbot
• Darracq
• Rootes
• Chrysler

Places

• Wolverhampton
• Ryton
• Coventry
• etc.

Technology

• Engines
• Carburetors
• Transmissions
• Suspension
• etc.

Events

• Le Mans
• Grand Prix
• Land Speed Records
• etc.

Every encyclopedia entry can link to related Sunbeam models and articles.

That gives the site a knowledge graph, rather than just a conventional blog.

And I would make the homepage very different

Rather than:

"Welcome to Sunbeam Cars — your source for classic car information..."

I'd make it immediately obvious that this is THE Sunbeam site.

Something more like:

SUNBEAM CARS

The history, cars, technology and people behind the Sunbeam marque.

Then perhaps:

EXPLORE SUNBEAM

[ ALPINE ] [ TIGER ] [ RAPIER ] [ STILETTO ]

followed by:

SUNBEAM THROUGH THE YEARS

A visual timeline.

Then:

THIS MONTH IN SUNBEAM HISTORY

Then:

SUNBEAM TECHNICAL LIBRARY

Then:

FEATURED SUNBEAM

Then:

FROM THE SUNBEAM COMMUNITY

Then:

SUNBEAM RACING

And finally a strong footer containing the site's major knowledge categories.

One other thought

I would not lock the site into "classic cars" either.

"Classic Sunbeam" is certainly a major part of the audience, but Sunbeam Cars is a much broader and more valuable identity.

The domain can encompass the entire history of Sunbeam automobiles, from the early cars through the Rootes-era models and competition cars.

That gives you room to build something that feels much more like:

The online encyclopedia and enthusiast resource for the Sunbeam marque

rather than:

"Another classic-car website."

That distinction is important.

And if that's the direction you're taking, I would actually rethink the site's architecture before you build too many Divi pages. The next useful step would be for us to create the actual SunbeamCars.com sitemap down to Level 2/3 pages, including which pages should exist now versus which ones you should leave for