I have 4' by 3" cast iron leaded Ty that has a 8" crack in it I want to remove the lead and replace it 4 X 3" Duel-Tite Gasket than install a 3" PVC piece of pipe to reconnect the tiolet.I was wondering If this was a good idea or did someone has another idea.

Sounds like a plan to me.

Just make sure those with impressionable minds aren't within earshot when you start this project.

I'm muttering a few choice invectives myself just thinking about it.

Seriously, were it possible for something to both suck and blow at the same time, then this project is it.

I'll include you in my prayers this evening.