the 200 4R would be easy... push the cross member back to the TH400 location, and bolt it up. No shaft mods, no drilling the frame, nuts and bolts job.
The tough (and expensive) part is getting it set up right.
Go to
www.bowtieoverdrives.com and check out what they have to say about setting up the TV cable. Even if your engine is stone stock, there is no cable set up made for that year carb and that kind of intake, so it may as well all be aftermarket stuff. Bow Tie Overdrives has the best kits and most comprehensive set up directions out there. Don't forget a lock up control kit too.
The TV cable and lock up kit will need to be done if you go with the 700 R4 or the 200 4R... the 200 is only easier to install, plus no drive shaft shop bill.
If the TV cable is not installed properly, your tranny will be dead in 20,000 miles or so. It may feel perfect by the seat of the pants, but if the line pressure is not dead nuts right, the tranny will not live.
The 700 verses 200 debates will go on for ever, much like the chevy verses ford verses dodge. Each has good points, bad points, and then some personal preferences thrown in on top.