Thanks for your response Don. I have a followup question for you.
I did understand your your t-shirt example but I think it's even more refined in our case. Since there are so many different variants, we do have to count them as different products, and we would like to avoid creating custom content right away (there's just so much we would have to create). I'm still thinking our perfect solution would be custom links but with a canonical tag pointing back to "www.cargoliner.com/products.php?did=10001".
Here's my solution based on your advise:
I'm going to keep my main page where people can sort to find there make, model, and year (www.cargoliner.com/products.php?did=10001).
Then I plan to have specific product pages per make, model, and year which will have duplicate content except for the make, model, and year searched and replaced. ie Jeep Wrangler 2015-2016 will be "www.cargoliner/products/jeep-wrangler-2015-2016" and in that page I will have a canonical tag point back to "www.cargoliner.com/products.php?did=10001" so I don't get hit with duplicate content.
After this and over the next 6-9 months, I plan to fill in all of the custom content for each product. Then I plan to remove the canonical tag once I have custom content on that page.
Does this sound like the correct approach?