On everything I've read on the subject, if you get your rods around .0027 to .0033 you will be fine, mains .0033 to .0038 gets you in the ballpark. .004 mains won't hurt, but you can run a half set of .001 under to tighten up .0005, coated bearings will get about .0002 more if it concerns you. My SB2 ended up with .0028 rods and .0033 mains. Small or large journal sizes won't matter (or big block), you still need minimum clearances to get a proper wedge of oil. Check this post.
http://speedtalk.com/forum/viewtopic...ring+clearance