It's impossible to set a carb up at the factory. They can get it close but the weight of the vehicle and it's uses will change the tuning. I highly recommend an air fuel gage. A fuel pressure gage would be helpful too. Is the intake manifold correct for vortec heads.
I have an small in my truck. 1st gear is useless and it shifts like an old dump truck. It's also 200+ lbs. I would go with the nv4500. The issue with it is it has electronic speedo so you'll have to a dress that.
I'm shaping from my small granny gear to an not 4th overdrive. Has anyone done this swap? It's going into a 1981 gmc 2500 2wd. Looking to use the mechanical clutch linkage. I know I have to cut a new hole in the floor, get an adapter yoke and new drive shaft. Any think else I should know?
Use a vacuum gage. If it's jumping around a lot you h ave a vacuum leak. When you installed the cam did you degree it? Put the #1 cylinder to tdc and mark where the line on the harmonic is on the tab. The tabs aren't always accurate. How did you set the valves?
I would take the carb off the intake and look in. If any of the dust gets into the motor it's shot. It will be like taking sand paper to the cylinders. Check the fuel lines going to the pump. They may not leak but if the pump draws air it won't draw fuel. Had it happen on my 78.
The u joints change how they vibrate or if they vibrate with the amount of road and speed of rotation. I had a ranger that drove fine till about 60 then sounded like it would tare itself apart. It would smooth out a bit as the speed increased. U joints were chewed up.