Anyone Know Lug Patterns? Cuase I don't...

[THE "10" SILVERADO]

I have always loved these type of wheels.....(see link) I don't know why but I have loved em and a lot of people hate them...(I guess I'm just different)

http://cgi.ebay.com/ebaymotors/ws/eB...43953....These seem overpriced (to me) but it's the best quality I could find to show you.

And I want to put some on my 77 Silverado 2x4. I have been trying to find out what size lug pattern I have (5 lug) but I can't find anything that goes back to 77. If I were to put these type of wheels on what kind of adapter would I have to get for them to fit on my truck?

Thanks