Straight 30 weight will be alright as well. I run mine on straight 30 all year round, and have never had a problem with it in the winter.
Don't put too much stock in the whole "don't use SM oil" thing, either. All motor oils are required to beckwards compatible. While there have been failures recently with the reduced ZDDP levels, but most of those can be traced back to poor workmanship on the rebuild, improper break in, or mismatched valvetrain parts. I put SM grade oil in flat tappet engines all the time, have yet to see one fail.
