200r4 or 700r4

[keith4909]

So I'm thinking of pulling my th400 to add an overdrive. I'm running a 474 Pontiac with about 450-460 hp and 550 plus tq. I have a 3.07 rear 12 bolt posi. I'm seeing either tranny for about 2200 to handle my power but which is best. I know the 700r4 has a lower first gear which would help my tall rear gear. I know the 200 will bolt right up. Any thoughts? What other parts will I need and how long do they typically take to swap out? Anything special I should know? Thank you