A pal of mine wants to weld in frame connectors in his 71 Road Runner. I don't know if he want to do it because it is the "trendy" thing to do, but I wonder if it is worth the effort.
I added them to my 70 Charger but I see this as an apples to oranges comparison. I have bigger torsion bars and sway bars, stiffer springs and better shocks. I run a much wider tire front and rear. He has essentially a stock suspension, 15x7 wheels and 235-60-15 tires. He rarely drives this car since he bought a 2013 Challenger R/T.
The car has the stock 383 with a mild cam upgrade, 727 and a 3.23 diff.
Opinions, please?

Oh yeah... I am asking because he wants to do this at my place on my car lift!

My '70 in original configuration, 318 auto, felt and drove better with the frame connectors... it was running 225/75/14 rubber at the time.

I think it will make a difference very noticeable. Are you talking the kind that bolt or weld just at the ends or the continuous weld to the floor contour? It was a huge difference on my Dart. I don't know what to say about the GTX because I never drove it enough to remember how it felt before I tore into it. I know it handles extremely well now and I have to assume part of that is due to the frame connectors.

It should be fine IMO. If it ran anything like my Dart did before I started tearing it down, you could probably feel the twist in the corners. If he does the subframe connectors with a nice pair of Bilsteins, he should have a very nice cruiser at the end of it.

These cars weren't the best when they were new and time hasn't done them any good. Even on skinny modern radials, I can't imagine them not being a noticeable improvement.

I hope that Bob doesn't read this post. It appears that I have no excuse NOT to help him...

Nope. They make a significant difference on any type of car. From a simple NVH persepctive, they eliminate rattles, pops, squeaks, poor door and window sealing ( wind whislting). Perfomancve wise, yeah, we've all read that.

Yep, I'm going to add them to every older car I buy from now on after adding the Hotchkis ones to my 69 Satellite wagon.

Worth it, worth it, worth it!

I went ahead and did it.
The 71 B body floor pan and frame rails (At least the rears) are different than my 1970 Charger. My rear rails hang down below the pan further, I did not have to cut as much out of the 3x3 steel that I used on mine.

Mine

I did get a few pix:

This car is owned by a guy that ordered it in the fall of 1970. It still has the original 383 in it!

The owner didn't want to cut into the floor to keep the connectors full depth. Because of this, I had to cut the connectors to the contour of the floorpan. I did re-box the areas that were cut down. I'm unsure of how effective they will be since they had to be cut down to almost 7/8" to remain flush to the Bottom of the frame rails front and rear. They are welded at three sides on each end.

I used the US Cartool kit on my Duster and then covered the undercarriage in Lizardskin SC

How about the twin-tubular Magnum Force SFCs? They appear to be slightly bent to stay close to the floor, very good ground clearance for low-cars, have an extra point of attachment near the middle. Anyone use these with satisfaction?

Also, I believe Magnum Force is introducing another similar tubular design (larger single tube) that wraps around the front crossmember and straddles the rear fram rail with a crossover attachment to the leaf spring bolts (syuch as where the Hotchkis units attach). MF offers this new design for A-bodies now,,, others to follow. Any comments about the MF units/design... vs the typical rectangular/box design (excluding the contoured floor weld-in types)?