There's almost always a way to add strength/stiffness. But when the loads are applied differently to the chassis, and may well be larger at the points where they are applied, you can't necessarily expect the same results. The load paths are different. There's not nearly as much "conventional wisdom" from where to start, so you're getting off a little more toward original chassis design and custom fabrication.

Unless you're going to compete in it at a moderately serious level (and the rules permit what you have in mind) I'd stick with carefully chosen performance parts for what you have. Don't just take the information that's provided in advertising literature and on web pages as your only source. Hunt down independent reviews and comparative tests if available. And ask specific questions here. Read Fred Puhn's "How To Make Your Car Handle".

It's not that the M II suspension is all that bad - in its original chassis it can be made to work quite well in spite of its shortcomings. Back in the 70's a good choice of essentially bolt-on suspension goodies could give you a car that on performance street tires would set faster run times at autocross than most other cars of the day on similar rubber. And about 0.85 lateral g's was available. BTDT. You'd need to do quite a bit more work to get similar results swapping this suspension into a car that's longer/wider/several hundred lbs heavier.


Norm

 

Like Norm and others have alluded. The II suspension is weaker than the classic suspension, so just beef up the classic suspension. Sounds like you have made that intelligent decision though. Why am I even here?

 

if you had a 64-70 i would say do it, but since you have the big engine bay 73, no need to remove the towers

 

atomsk the 67-70 both ford big blocks will bolt in .when i autocross my mustang since i have coil overs front and rear it moved me up to the mod x class which makes it harder to win.opentrackers parts keep it oem ford desgined so you wont get stuck racing in a harder class