coil spring front
Bullshit . and it never ends
No, that's not bullshit. There are multiple instances where coil-over converted Mopars have gone head to head with torsion bar equipped Mopars and lost on the AutoX track. Torsion bar Mopars have bested new 3 series BMW's on the same track, with the same driver, with the same tires.
The coilover conversions on the market are all modified MII suspensions. There's really nothing magic about a coil-over, it's just a spring and a shock. I've posted lists of parts MANY times showing that you can replace everything in the torsion bar system with brand new parts and have just as much or more adjustability than the coil over conversions for less money. If the OP would like I can do it here as well, but I know you've seen it before.
The bottom line is that all suspension designs have their pros and cons. Coil over systems are no different. They have some advantages compared to a torsion bar based system and they have some disadvantages. But with any coil over conversion you have the challenge of placing the suspension loads on the chassis in a place where the chassis was not designed to handle those suspension loads. Torsion bar cars were designed to carry all the suspension loads in the K member and the torsion bar crossmember. Not on the front rails where coil over conversions place them. And that's not just an issue at the mounting points, that's an issue with how the frame rails are attached to the rest of the chassis.
It really depends on how the OP plans on using his car, for some applications (engine swaps, for example) a coil over conversion will have some nice features. But they're not some magic fix all, and like any aftermarket parts you have to consider what other modifications are necessary to make them work their best (like reinforcing the chassis to brace the frame rails to the cowl/body). And just like any suspension system they need to be tuned to fit the application, and better tuning is more important than the kind of spring you have.
But if you would like to provide the suspension geometry plots to show why a modified MII suspension is so much better than a modified torsion bar suspension I'd love to see them.
