Update:

The glue I used to glue the dust caps back on the speakers seems to have dried, so all the speakers are ready to go back in the cab, on Tuesday this coming week, I'll pay a visit to my local Jaycar Electronics store and see if they have any acoustic dampening material in stock, and I'll buy as many rolls of it I can, next stop will be to my local Bunnings store for a set of new castors, and some nuts, bolts, and washers for attaching them to the cab, will also buy a new cordless drill while I'm at it.