[Oldsguy]

I just went through this when I had the driveshaft modified to fit my engine/vehicle combination. I took the driveshaft to a place that does axles, driveshafts, constant velocity joints, etc for trucks and all sorts of vehicles. Anyway, we had some initial troube getting the driveshaft to fit after they modified it the first time (perhaps due to a measurement error on my part) and they were saying they wanted about 1.5 to 2 inches of space to allow for the rear suspension/axle to move up and down. I ended up with 1.5 inches of space. Hope this helps you.