Gas tank conversion help needed

[revitout]

Hi , I am converting from LPG back to petrol. I have no parts what so ever so need to by everything new. (from tank brackets to carb) The trouble is I don't know whether to buy 73-78 parts or 79-87 parts. The truck is a mid eighties double cab on a 76 suburban chassis. I think the short-bed deck is mid eighties, but how can I tell? It has two filler doors, one each side so I want I to put dual tanks in.
I need to know which tanks to get year wise (what is the difference) and what filler components to get to suit the tank Also which sender and selection valve because these are listed with number of different outlets.
Idea also would be if there is someone here who can sell me all the bits and send them to New Zealand that would work then I know I have got the correct stuff.
Cheers