DO NOT use regular oil, the govt. has taken a lot of additives out of it and it will wipe your cam out on break in, use either shell rotella or vavoline conventional race oil, those still have zinc and other additives in them, and i always use 30wt for my break ins.
5/30 should be OK. I just have this thing that I've used 10/30 Valvoline for ever and never had any problems so I stick with it.
Modern rings with the correct bore finish are not much of a concern.
The cam is the major break in concern if it is not a roller.
If you have a flat tappet cam make sure that you are using an oil that has zinc in it. 10/30 Valvoline VR1 or diesel oil Add a can of GM E.O.S. (engine oil suppliment)for break in. Joe Gibbs Lubricants has a break in oil now also.
To check out some oil stuff look at this http://www.atis.net/oil_faq.html
I go with Valvoline straight 30w with EOS from GM- I always run valoline in my cars and Rotella Synthetic Diesle in my bikes. And I will NEVER touch penzoil- after seeing the crap that build up from it I wouldn't put it in my nieghbor's lawnmower.
ive always had the best luck with pennzoil, anything else it burns oil, pennzoil was the cleanest also i had castrol for about 30,000 miles and it stained the motor black inside. ill probably use pennzoil, would the longlife diesel oil be what i use for break in? or straight weight because all straight weight pennzoil still have the Z7 additive. and could anyone tell me what is in the Z7 additive package?