Front perch help needed

I'm beginning to build the 2x4 chassis for my pickup and need a bit of help(alot actually).

I plan on running a CE 4" drop I beam axle with the spring over the top. Im trying to mock up the frame but have no idea on the height above the ground i should design the front spring perch at. Im using 24" tall tires and running a big block and turbo 400, what do u all have for a perch height above the ground?

I'll be asking a lot of questions from now till xmas as i really want to get the chassis cut and welded up, which ive never done before either.

 

You need to know how much weight is on the spring and how stiff it is. You can figure the heigth of the spring ends by mocking up your parts. Put a spindle on the axle and put a wheel on it. Install a bat wing/radius rod and put in a perch bolt. The end of the spring will be 1" more toward the axle because of the shackles. If you tell me the spring you are using and some info on the car, I would guess how much your spring will compress. You know how much arch is in it now so the loaded heigth of the spring center can be found.

 

Depends on the exact spring. Posies springs. I think buying a spring with the correct center to center dimension is critical.
I'm at a similar point,I plan on buying a spring based on the perch dim. of the axle.Once I've got the spring in my hot little hands i'll compress the spring until I get the center to center dim specified in the chart and measure the height of the arch.Some simple math will tell me what I need to know.
An interesting frame building site is:The Antidote

 

I built a spring testing device. It allowed me to calculate the spring rate and the deflection with load. I tested every spring I could.I can probably give you the spring rate of the spring that you have and predict the compressed drop.

 

Guess I need to order the front end parts and mock it up, going to be difficult to tell the weight on the front end tho.

I was looking at those posies springs too, guess I'll try giving him a call, they probably have some good comparisons.

Wanted to get on with cutting the rails for the front end kickup but I'll hafta wait.

I feel like Capt. Kirk here, going where I've never gone before....