Personally, I order
Amsoil over the Internet. I use their 15W50 racing series due to the high content of lubricants as I'm running a solid flat tappet cam. Off the shelf organic oils seem to lack sufficient lubricants due to EPA regulations. If you're running a solid cam, I think a specialty
oil is a good course to take. I'm told you need 3K or more miles on your engine before you convert to
synthetic or you may have break-in problems.