I use stock kickdown with my air gap intake and 750 street demon carb. There's a suprising amount of adjustability in the stock pieces. It will take some trial and error to get it right though.
Are you sure the converter is the factory original? The torque converter is a reactive device. The more power the engine makes the higher the converter stall speed will "flash". Likewise when an engine declines in power the converter won't stall very high. Make sure the engine is running at peak...
A few years back I did screw together a 440 stroker 493 six pack with 440source aluminum stealth heads="chinesium". Those things needed around $600 to equalize valve heights, fix rocker stand geometry and valve guides but new they cost $995. They might have worked OK out the box..?? I've heard...
If it were mine I wouldn't run Eddy heads either. Their quality control, at least on small block Mopar heads, is lousy in my view. Mine needed a LOT of rework to be right. I'm not as well-versed in big block aftermarket stuff, though.
While I haven't done this myself, you will gain a little over 1 point of compression if you go from an 88cc chamber to a 75cc chamber on a stock stroke 440. The real question is how far below deck are the pistons. If it's an RV motor, I wouldn't be surprised if the pistons are down at least .080...
I imagine you can improve/fix what you have now but with stock stuff it will never drive like a new car-if that's what you're after. Does it have power steering? Mine has power assist and drives fairly straight at slower speeds. I once drove an E-body with manual steering and the car wandered...
Wow, very nice Challenger! I think it's cool to see one stock and really nice. Me personally, I would leave it the way it sits and find something else to modify. Does it drive nice down the road and run strong? My experience with aftermarket stuff has been a mixed bag of misery, re-engineering...
So the parts book show 3698355 fitting ALL Thermoquad setups no matter if it's 340/400/440. I'm a little surprised-I would think there would be different rod styles and lengths.