Well, the priority is to still get the oiling system right. Won't matter if it's a brand new block if it can't get any
oil. With a modern style suspension, a car is very well capable of pulling the
oil away from the pickup.
As far as blocks, I wouldn't spend a bunch of money on a "new" old block. However, that just depends on your budget. Pond is the best deal going and the good thing is that if you ever decide to push the hp, you won't have to worry about splitting the cam tunnel. The aluminum block is another $1000 on top of the cast iron price, so again, it's up to your budget.
There are no issues with driving day to day with an aluminum block. OEM manufacturers do it daily a million times over. You just run a good
oil, get the thing warm before you beat on it (you should do that anyway), and drive like normal.
How much can you spend? I personally would skip the old blocks altogether if you plan on racing.