The 200 cu. in. 6 cylinder engine is a very good and reliable engine. It has 7 main bearings. Yes, you are stuck with the integrated intake manifold but there are modifications you can make to this engine. Here is a website you can check out. Ford Six Performance Home/Index
I own a 66 coupe with the 200 cu. in. 6 cylinder and 3 speed manual transmission. It runs great in traffic and on the Interstate. With gas prices going up and up I like the idea that I get over 20 mpg. Also, at car shows I get many comments and questions on my six. Everyone has seen a 289/302 in a Mustang but many people didn't know or don't remember that many Mustangs were sold with a six cylinder engine. My opinion - keep the six and enjoy the car.