That's one thing I am still working on with my 3.4 swap and 4:88 gears. I am not sure I have the vacuum supply correct. It comes on but jumping all over. I think I have the cable adjuster correct. Made my own custom cable because the throttle body is on the other side of the motor.

If you are doing bushings. I would suggest getting new springs. I got mine re arched and added one leaf. The stock suspension was never meant to carry the weight of a motorhome. I still have the factory air bags with that. It now rides level even with a full load and big box on the back.

I am running a 2002,3.4 with a 1995 computer. Stock automatic (1992) . Single exhaust,one cat . 4:88 gears. I drive it most of the time in overdrive. I can feel the torque converter lock up on small grades. I do shut off the overdrive when in the mountains. I drive around 60 or a little above. I was a truck driver for 45 years. That's where you get the best millage. When I push a l hard going over the mountain I get about 12.5.  If I take it easy I get about 14.5 to 15. No such thing as long flat road in Central Oregon. I would have to go east for that. I can easily go 70 but the handling go away on narrow two lane road. My wife and I love this rig. It's been some work but fun.