Custom Wheel size on a 67' Back spacing Help!

[Flat Rock Mayor]

Looking to put new wheels on my 67' c-10. Was planning on purchasing American Racing BLVD. 18"s. The 9.5" wide show a 5.25" back spacing which is exactly how much room i have not even allowing for the tire. Noticed most run 20"s by 10"s and i am wondering how they fit? Am i looking at something wrong. Your thoughts and suggestions please!

[SeTx67]

From what I understand the 67-69's have a narrower rear end than the 70-72's. Some guys run a spacer or you could get custom wheels with whatever backspace you need but that's pricey. I'm in the same dilemma but I decided to redo my suspension and brakes first
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[Flat Rock Mayor]

Thanks for the reply and that's what I understood as well. I hadn't thought about spacers though. Will have to research that one. On the axles what I have found is that 65-69 have a 30 3/4, 70 has a 31 1/2 and the 71-72's run a 31 3/8 axle. I am assuming that extra 5/8" is what is allowing them to tun the 10" wide wheels. Does any one know the pro's / con's of the spacers?