My old toilet has a 10" center while the new one has a 12" center. I can get an angled flange that will make up the 2" needed. How do I connect/cut the original cast iron pipe and attach the new plastic angled flange?

Is your house on concrete slab or raised foundation ?

In any case, it is not an easy job to install off-set flange but it can be done. That is especially true in case of concrete slab.

Lot (lot) easier is to purchase TOTO toilet . What it is - is a regular toilet and it comes with special connecting base to fit your existing rough-in. It is more expensive but the job can be done in 15 minutes. Besides, TOTO are considered to be one of the best toilets on market.