what I require in the admin section is:
1. Manufacturers to be multi-selectable like categories
2. Option to input appliance model names and appliance GC number. Similar to catalog/manufacturers in standard opencart except you should have field for model name, model GC number and then a manufacturer dropdown select box to choose which manufacturer the model belongs to. Appliance model number and appliance GC number are always linked together. These could then be selected in product / links/page
2. In catalog/product details tab where you add/edit product details, I need the following options, which are not standard to Opencart:-
a. Option to choose manufacturer from multi-select box
b. Multi-selectable dropdown like in categories to choose Appliance model number and Appliance GC number. Since Appliance model number and Appliance GC number are linked (as in note 2 above), then you would only need to choose appliance model number and the GC number would automatically link. Also the only models that should display is the model numbers belonging to the manufacturers selected (option a above).