Leaf Spring Rate Question

[T. Turtle]

Good Day All,

on the build sub-forum I started a general thread about my car (64 Mercury Comet Caliente) but I have a more specific issue I want to ask about:

I decided to retain the basic leaf spring suspension at the rear but adding a Mike Maier Panhard rod set up. I also have his Mustang springs but those are way too short and flat for my car hence lowering it by something ridiculous like 5" which is totally impractical (see pics. Yes we did drop the transmission jack to test and the spring did not move). Short of starting to brutally cut things I do not see how I could use them so they'll be up for grabs - there should be enough Mustang guys even here in the EU to want a set I'm sure. So the issue is what to use. As some here may know you can get 5-leaf heavy duty Scott Drake springs, either mid eye which supposedly retains the original ride height or a 5-leaf with the standard eye location which should raise the car by about an inch (those are referred to by Scott Drake as C4DZ-5560-HD). My thinking is I'd rather avoid the same thing happening twice and to me it's easier to use a lowering block to make sure the car sits at an optimal level. Oh and I can get them from the UK which saves a huge hassle with shipping from the US, paying import duties etc.



My questions are:

• according to my information, the C4DZ-5560-HD springs have a spring rate of 165 lb/inch. Bearing in mind my car is intended for fast road driving only, does that sound like a too high a rate? My intention is to run either 16" or 17" wheels whilst keeping the original overall diameter, so there will be some tire compliance. I most likely will take the spring apart and put some grease between the leaves to ensure no friction.
• I did a search on leaf suspension and a Panhard rod combo threads here and it seems the prevailing opinion is that there are benefits to having such a set up but a suggestion which was made was to use Afco leaf pivots to avoid bind between the Panhard rod and the spring as both move through their arcs. Any thoughts?

Thanks in advance.

Cheers
T