The NV4500 transmission is your best bet for transforming your 1st Gen Dodge into a machine that is as good as new. Its performance is comparably better than the Getrag G360 that your truck already has. It is a robust, durable, and reliable 5-speed transmission system found in today's trucks, which is probably why it is such a good option for your older (and precious) pickup truck. 1-ton trucks like the Ford ZF have it, and it is also a solid option for car enthusiasts looking to step up their game and create extreme Broncos, Jeeps, and other heavy-duty off-road trucks. This swap will take you a few days, so clear up your schedule, and get started.
You will need a conversion package
If you check with a typical transmission retailer they will show that their NV4500 transmission is not compatible with your vehicle as you can see here,
Regardless, however, the NV4500 transmission will perform great with your engine. All it needs is a conversion package. This package is essentially all the new components required to install a new generation transmission system into your truck. Your truck, being a manual drive, will already have a few things compatible with the NV4500, such as the pedals and the hole cut for the shifter. Your truck's clutch's hydraulic system is also the same, and will only be bolted differently on the NV4500 bell housing. However, the difference in generations means that a few of your truck's parts will be modified, repositioned, or replaced altogether. While obtaining your conversion pack, consider:
The required driveshaft modifications
Your desired transmission length will be slightly different than the one in your truck, which means that you might have to modify your drive shafts. However, since the difference in length between the two systems' transmissions is about 1/4 of an inch, you can use the same driveshaft because the slip yokes will account for the length difference. Start by installing your new transmission and transfer case. From there, you should be able to determine the best way to proceed. A local driveshaft shop will easily perform any needed modifications for you for anywhere between $200 and $250 and should take a week or two to complete.
You will require a second-gen adaptor plate. This plate is close to 3/4 -inch thicker than that of your Getrag G360, and will therefore not be compatible with the NV4500. This should come with your kit or you can source one from the NV4600.
Your 1st Gen will require a cross member swap since an NV4500 one is significantly different from what your truck already has. The new one will come with new bolts.
The floor plate
The hole in the floorboard for the shifter has to be repositioned to match its new position on the NV4500. For the Getrag G360, the shifter goes through the floorboard from the front of the transmission, while on the NV4500, it goes through from the rear end of it. If you choose to cut your floor plate rather than replace it, the cut should be 4 1/2 inches back from the original position.
The 4WD shifter bracket
The NV4500 has a bracket attached to the right side of the bell housing from your 4WD shifter. This bracket has a linkage between itself and the transfer case. This bracket can be ordered online.
The best way to start your swap is by installing your new Second Generation adaptor plate. Ensure that the adaptor plate bolts are tight before proceeding to attach the flywheel to the crank flange wire wheel. For a reliable connection, you can use heavy-duty glue on your flywheel bolts and the crank flange. Should you need to get everything apart, a sledgehammer should undo the bonding.
Attach your clutch system: start by wiping down the surfaces on the flywheel and the clutch pressure plate to remove residual oil. Your clutch disc should have the flywheel side and the pressure plate side marked to guide you, so start with the disc, followed by the alignment tool, and finally, the pressure plate and the required bolts. Again, ensure there is glue on the bolts for safety.
Install the transmission system up to the truck's adapter plate, followed by a starter, and the transfer case. You should also be able to install the rear driveshaft, the 4WD linkage with its bracket, the cross member mount on the NV4500 tail housing, and the front driveshaft in that order for ease of work.
This guide should help give you the know-how and the tools to pool for the job. However, since you are replacing an entirely different transmission system into your First Gen, quite a degree of 'make it fit' will be required