Anyone using these on a street/strip car ? They look pretty stiff, do they recommend a snubber like the S/S Mopar leafs ?

They do not need a snubber since they are super stiff on the front segment.

I have 'em on my street/strip car and they are probably just a tad stiffer in ride feel as the OLD original SS springs of yore.

Make sure to ask for the desired ride height. There will probably be some body lean /sag towards the passenger side because of the extra stiffness on the right rear side just like the OLD original SS springs did.
They work amazingly from just the very little that I have used them last year. Car response is zappy to say the least, but in all honesty, this may be attributed to the improved new Ultimate Lenny convertor spinning in the bell.
Probably more potential with proper shock adjustment. Adjustable correct length rear shocks are a must.

They come clamped on the right positions on the front segment and also have solid aluminum bushings with a roller sleeve in 'em.

They are heavy. Had them on an F body. They do require a fair amount of tuning if you are making some good power. Switched to Cal Trac. Lighter, easy to dial in and they are very streetable.

They are just as heavier by 5 lbs more or less compared to the SS springs. Believe you me, I have weighed them both.
SS springs are heavy indeed, but so are the majority of other multi leaf springs. A mono spring and Cal-trac will be lighter but will differ from SOME cars to another in feel, performance and ride height.
Tuning is a given as mentioned, but so is with every other part of a car with decent horses on tap.

Can these be used WITHOUT a pinion snubber and still control windup? I have 456/457 SS springs right now and my truck sourced Dana doesn't have a snubber provision. 4° nose down and it's still hitting the transmission tunnel at launch.

A good front segmented spring like Launchers will not need the snub just because the segment itself will act as a ladder bar from its stiffness like a Caltrac and not let the rear wind around as much and use that energy/movement to plant the tires.

Some cats on here have clamped the front segments of SS/springs and or regular HD springs to achieve the same affect and tossed the snubber with good results.
Again, a good long shock with low resistance on the up swing and heavy resistance on the down swing will do wonders. Adjustable long shocks will even do wonders with an SS spring.

GY3. I would experiment with some front clamps to stiffen and removal of some rear clamps to see how it relieves the hitting which is not such a good thing. Sometimes even with a snubber, a rear will smack the tunnel pretty hard and start tearing it apart.

Another trick if you do insist on a snubber with your situation with no snubber provision is to fabricate a HD plate that mounts underneath the floor with a snubber attached to it pointing downward to snatch the rising rear.

GY3.

What type front spring eye bushings do you have?
Are they tight or have a little play to allow swing?

In all respect, your car is scootin'.

In all fairness to TRI CITY. Some of the most scienced out leaf spring cars on the planet are NHRA Stockers. 99% of them use Cal Tracs. The launcher springs were better than SS springs but that is old tech. Is this car destined to be a street strip car? The launchers will make it ride like a lumber wagon.

The rubber bushings that come with the SS springs.

I looked at a friend's Cal-Tracs last night and they come with solid aluminum replacement bushings. Not sure how that affects street manners?

I experimented with the clamps and that got me from 1.59 to 1.54. I thought about doing a snubber pointing down from the floor, too, using an upper control arm bumper that I removed.

Keep your rear shackle spring eye bushings as rubber or at best, polyurethane.
Change the fronts to solid aluminum with a metal bushing sleeve. Tighten only just beyond snug to allow for some swinging and that pup should plant them good.
In most cases including mine, I have noticed nothing in street driving as far as ride quality or clacking noises. In some remote cases, you will hear a small clack in take off, but that is common with a solid front bushing. There is no play and the energy finds its most straightest line of application, the rear tires.
Yes, to answer the addish of old school vs new, cal's are the new kid on the block when it comes to every hundredth in serious Super stock competition, but for most street mild and border line wild combo's, the old US made, Canada made SS's or Launchers worked darn well enough to surprise some heads.
While the cal's allow for some easy on track tuning and weight loss, we all have bared witness to some deep nine second stockers on SS's even on the street here.

Rubber bushings allow some flex, dampen noise & harshness, but the side effect is some changing of centers and binding at pivot points. None of those side effects matter much for street use.
When you're chasing every performance advantage you can get, eliminating flex, bind, & such allows those parts to move more freely and consistently, but in the case of rubber bushings, their insulating properties would be lost by replacing them with what's essentially solid material.
The rubber's also a bit more forgiving as far as lubrication (or lack of).

Yes. lube is most important with solid eyes.

I doesn't.

RMCHGR What do you mean?
Cal's don't affect street manners or it don't come with solid bushings?

Sorry, should have clarified.

Caltracs DO come with aluminum bushings.

Caltracs DO NOT effect street driving in a negative way, at least in my experience. In fact, the ride quality in my Duster was a little better when I replaced my S/S springs with Caltracs.