Exposed filters with dropdown selections
The problem here is that the fields are custom text fields. If the "product type" field was of the type "List (text)" instead it would be a drop down in Views when exposed.

Maybe the product type would be good to have as taxonomy terms instead? Then product types could easy be added to the vocabulary as the site grows. The field in your content type would then be a "Term reference" to the Taxonomy vocabulary product type. If the product types rarely or never change you could stick with "List (text)"

I would probably make the field year into a date field or taxomomy, or list (integer).

I hope you see where I am trying to go here, the fields needs to be of the correct type for Views to be able to interpret the fields correctly and "automatically" give you dropdowns when the filters are exposed etc.