I'm thinking about picking up a 72 Dodge D200. It has a 400. Has anyone had much experience with this engine. Will it be easy for me to increase it's power? I think stock it only puts out about 200hp and would like more.

 

It will respond to modifications like any engine. The 400 is a very strong block. You could make a nice 500 hp street motor if that is what you want..
To start a cam, intake and carb change would wake it up.

 

Depending on what you have for a tranny and rear axle (probably a dana 60), there are other items that can really help wake up that motor too. Limited slip in the rear axle so that both tires put power to the ground rather than one, a shift kit and stall convertor that works at the start of the power band of the cam (if you have a auto) or a really good clutch (if you have a manual).

Headers that match your target power band will greatly help too.

 

x2
this motor is what i have in my mud truck and great motor good cam int and carb if you can get 383 mag heads nice add on and keep oil pressure i run 100 psi and run 8000 rpm all day