Walter,
Welcome to the forum.
Larry,
I don't think anyone is totally expert on things but collectively we can usually help.
I can't give exact dimensions but an idea of how things work. Maybe someone will have some good suggestions.
Your BJ8 should have a split choke cable & housing, one knob pulls two wires. The single to two wire transition is a splitting block at the firewall. The carb end of each wire housing is anchored to a bracket on a carb. The inner wires are attached to choke operating levers on the carbs. There is a clamp or stop near the end of each wire which sets the effective wire length.
The first part of the operating lever movement operates a fast idle cam only. As it moves further, it pulls the jet down to enrich the mixture.
To adjust;
With the choke knob pushed fully in, the wire end stops at the levers should be placed so that there is about 1/16" of free play before the stop (wire) begins to pull on the lever. (See problem below before proceeding) As you begin to pull the knob out the fast idle cam will engage. Further movement should actually lower the jet. There is a fast idle setting screw that bears on the cam & it should be set to give around 1200 rpm fast idle when the choke is pulled. There are several screws, don't turn the wrong ones. There are a slow running valve (idle mixture screw) a jet adjusting screw, & the fast idle screw.
One problem to watch for is that if the cables from splitter block to carbs have too much friction, when you push the knob back in, the outer part of the cables pops out of the splitter block instead of the wires & levers returning to the unchoke position. This drastically reduces the amount of choke wire travel & can result in poor running or the wire stops being set incorrectly.
One "fix' is to put coil compression springs around the wire ends so that one end pushes on the outer cable anchor point & the other pushes on the choke operating lever. I've heard of using a spring out of an old ball point pen. Others have found a way to more securely anchor the cable housings at the firewall end. Removing as much friction from the cables as possible helps.
D