Hi I´we got an 67 dart with the slant six and I´m forced to switch the engine in it. And about to buy an 73 model six.
I´m wondering what is the difference between the pre 71 engine the 145hp and the post 71 engines 100hp. how are the hp decreased in the later version and is it possible to get the hp with just switching parts between the 2 engines(if witch ones?). Or is it just easier 2 put performance parts on the 73 engine? Anyone with an answer?

The main difference is in the rating system. Early numbers are gross horsepower, as opposed to net ratings of the later engines. As I understand it, the engine output didn't really change in that time period.
The methods of testing, conditions, and what accessories are present have changed over the years and keep changing.

_________________
"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Thnx for clearing that up, was wondering when I saw the specs that there was a 30hp loss. But didn´t find any big mechanical differences between the engines. Thought it was just to get better fuel economy.

The engines' power outputs are similar. You can use the '67 intake manifold if you'd rather not have EGR. If your '67 car has an automatic transmission, you will need the 1/8" annular adaptor ring to install in the '73 engine's crankshaft counterbore. It can be had from Pat Blais, tflitepatty@verizon.net .

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.