If you need 5 spare engines, your doing it wrong. I think the only reason you had issues was from Oil surge.. Fix that and your golden..
My motor has done quite a few passes, LOTS AND LOTS of street rape and daily driver duty over the last 6 years... its made between 420whp and 800whp its entire life, i have only had 1 issue with it ( due to my awesome tuning skills) lost a cheap cometic head gasket.
I guess being that your already setup with an RB, i just don't understand the hassle your going to go thru swapping power plants.. Might be a little cheaper but worth the hassle?? Not in my eyes!!!
But i suppose i'm Biased i have a hard on for RB engines..