I always hate to see anyone using concrete as a support, especially on uneven ground as it can easily crack. I think thick blocks of wood are far better for that.
I've only ever pulled an engine 'outside' like that once, never again, it was hell so kudos to you for making it work.
Good luck with the swap.
Anything I might say is probably worth what you paid for it, so treat it accordingly!
[This message has been edited by ltlfrari (edited 08-25-2015).]