I am swapping a Gen3 5.7 and a NAG1 into a 58 Plaza. I live in Michigan and our roads are awful. Driving this car with it's stock suspension, that is wore out, just is not good .Deciding if I should rebuild stock, or do the Dakota front end .I know a couple have done this and have a few threads on this site. My question is, was it worth it? Was it that much of an improvement over the stock? Not racing it or anything, just burnouts and average driving

Personally, It would be easier to rebuild the stock suspension. (https://www.oldmoparts.com/. But, if your going through with modernizing the drivetrain.

Maybe the hemi will fit in a crown victoria frame. Lot better ride. The dakota graft is a good idea also.

I have a 59 dodge custom royal that I'm going to try and add some extra caster, by seeing if the newer upper control arms can be used. If so, I may buy some aftermarket a-arms that have more caster built into them.

It's got a torsion bar front suspension, no reason why it can't do the job if properly rebuilt.

https://www.moparmall.com/1957-59-Mopar-Front-Suspension-Steering-p/qg-67712.htm

https://p-s-t.com/i-23159111-original-performance-standard-front-end-kit.html#!model%3DSAVOY%7C%7Cmake%3DPLYMOUTH%7C%7Cyear%3D1958%7C%7Csubmodel%3DBASE

Firmfeel makes custom torsion bars. Not real cheap, but not a lot more than the off the shelf stuff.

https://firmfeel.com/collections/torsion-bars/products/custom-torsion-bars

A good set of shocks will help too. You may need to find the collapsed and extended lengths and search about for something more modern that can be made to fit. That's how I got a set of performance gas charged shocks for my 51 Plymouth.

Tires though, they make the difference.

If your existing frame is in good shape, and the suspension only need to be rebuilt, and the brakes updated to disc brakes (disc conversions used to be available) And (the big one) you are OK with the 57-60 Mopar power steering I would not swap in a Dakota subframe. (I have done a lot of Dakota swaps).

The difference between going from the torsion bars front suspension to a Dakota clip won't make enough difference to warrant the amount of work needed, as long as your frame and suspension are not all bent up or rotted and you are OK with the 57-60 Mopar power steering (am I making that point clear enough?)

If, on the other hand you really don't like that Mopar 57-60 power steering (or it needs to be rebuilt), that might make the extra work of installing a Dakota front clip worthy while. If that OEM power steering needs to be rebuilt (big $$$), or doesn't work the way you like it, there are not many options to replace it with because of those torsion bars. That OEM power steering was only used from 57-60 and is a major pain to remove from the car. Between the heater and the PS, putting that 5.7 in My son's wagon not an easy task, but he sure likes it now.

My son has a 57 Dodge wagon with a 5.7 Hemi, auto OD trans and the original rebuilt front suspension, with power steering and a disc brake conversion (his came with the car when he bought it) and it works well. We did adapt a modern steering wheel and turn signal switch onto the upper steering column (a lot of work as well), and he has added a modern front sway bar.

I would consider swapping a M-Body sub with the transverse suspension.

I quit doing them back in the early 1990s when better options became available. With the frame set up under those 58 Mopars I would never put an F, M & J body suspension on one of those cars. You would be starting from scratch, you have to build a frame to bolt the crossmember onto. I would do a Dakota clip long before I'd even consider an M body crossmember. I have done several of both.