how to make these astro wheels fit?

Hi guys, I am not very familiar with wheel mathematics so here is my question, I have a 63 mercury comet with the stock 4 lug wheels, I want to run these astro supreme wheels but I do not want to do the 5 lug swap yet, what would I need to do to make them fit with wheel adapters? I think my standard backspacing is 4 inches stock but I am not too positive, would I need to get a certain width adapter? any help is greatly appreciated... here are the wheels in question

http://cgi.ebay.com/ebaymotors/13-S...Q5fTruckQ5fPartsQ5fAccessories#ht_4318wt_1167

-Julio---

 

The "MINIMUM" width of the adapt is the length of the stud sticking out. Add that to the backspacing to put the wheel in the same posistion as before, (assuming the both wheel widths are the same) and see what the seller has to offer in that range.

 

Do the drum and axle swap or stick the ugly wheels in the shed and wait until you can do it right. The money you spent on the adapters would go a long way towards getting the 4 to 5 lug swap done.