This more complex than it seems. I simplified things a lot for this specific posting question.
The only Pitman arm available for that Flaming River box is only 4.5" center to center. The box also uses a different spline pattern than the original Chevy factory box.
The original Chevy factory box output shaft has a 1" nominal diameter splined shaft, with 36 splines = 32 "regular" splines plus 4 of what I have now learned are called "master splines". The "master splines" are female on the output shaft, to accept 4 "male" master splines on the Pitman arm!
The Flaming River box has a 13/16" nominal diameter splined shaft, with the same 32+4 master spline pattern. So, a "Chevy pattern" splined Pitman would have too large a nominal diameter.
The BOTTOM end of a Pitman arm also varies. On the stock Chevy 55 1st Edition, it is a tapered hole that fits onto a tapered shaft on the balljoint on the drag link. I have the dimensions for that tapered hole.
The LENGTH of a Pitman arm also varies, and is CRITICAL to ensure both correct "leverage" and even more importantly, to ensure no increase in "bumpsteer" when the truck suspension compresses or extends!
Finally, every Pitman arm has those 4 master splines "clocked" at different orientations to match both the steering box and the vehicle! This is to ensure that the steering box is at "center" when the wheels point straight ahead (for minimized wander and tighest steering wheel), and so that the drag link is not forward or backward of its intended position under driving conditions, as displacement of it will greatly (and badly) effect bumpsteer and turning limits left and right, and in extreme cases, could bind the steering under hard turns!
So, once you change ANYTHING, you need to ensure that you are either follopwing someone else's already proven solution, or you need to very carefully learn enough to "design" your own solution that "follows all the rules'. I can't find anyone else, at least yet, who has done an LS series engine into an AD truck AND has kept the stock front axle, so I am by necessity "a pioneer" here. I am proceeding very carefully, and Randy is very experienced, but it takes time and effort and lots of mathematics, because there is lots of 3-dimensional placement involved. I have spent HOURS on the mathematics today (including lots of trigonemtry!) to ensure we stay inside the correct dimensional envelope.
I can tell you this: those GM engineers who designed the original system were VERY good. They came up with a solutin that met all the constraints while remaining VERY simple overall once installed. The design was elegant. It just won't accept a wide engine.
Jim G
