I have done this very swap to my truck. For the 94, you will want a 92-95 model bellhousing that has the external slave cylinder. I broke 3 NV3500’s (technically I broke two, and damaged the 3rd one) because my engine was built to towing and has way more than 300 ft lbs of torque the NV3500 is rated for.
I have an ECSB Z71, and I didn’t have to do any driveshaft modifications my aluminum one fit just like a glove, the transmission mount and crossmember fit perfectly as well. My transmission was from a 93 1 ton, so I didn’t have to do what you’re dealing with.
Now me personally, I like the external slave cylinder, because you don’t have to remove the transmission to access it.
I am running a ceramic disc clutch in mine to handle the power. My stock replacement slave cylinder works fine with it. The only thing I noticed was the NV4500 transmission makes a little more noise than the half ton transmission does, nothing horrible, but still noteworthy. You lose having synchronizers in 1st and Reverse with this transmission, so that is another thing to remember.
The reverse light connection is a ***** to get to with the transmission installed, so I would recommend connecting it before fully installing the transmission.
If you already knew all the fine details about the NV4500 I apologize, but if you didn’t know, now you do.