Washer drain and vent pipe
It's not going to be that simple. Unless you support the pipe above where you want to put the rubber boot, it's likely going to come crashing down. Depending on what's above, you might be better off cutting the cast iron where you want, and replacing everything above the cut with PVC/ABS. Without knowing more about what's above this, and what else ties into that pipe, there's no way to provide an accurate answer. 

I will say that the rubber boot, is likely not the best course of action.




Remove the galvanized pipe.
Use a chain break to cut the cast iron a bit lower than you planned.
Install a Fernco coupling to transition from cast iron to PVC/ABS.
Finish the plumbing in PVC/ABS, including the tee for the standpipe trap arm. 
Properly support PVC/ABS plumbing.




Make sure the trap arm for the standpipe is not too long for the size of pipe you're using (2" pipe = 8' max. developed length trap arm 1.5" = 6'). Also make sure the drain has the proper slope.