Does it have ball joints or kingpins in the front, i bet kingpins, but there are some 78's with ball joints? It should also be drum brakes. I would start with, because I am on mine, converting the front over to ball joints and disc using control arms built be Beebani (on here and on Ratsun) and hardbody/720 parts. There really isn't anything wrong with kingpin suspension, and you can leave it, but it is difficult to find parts for. Bagging a torsion truck is pretty simple. On a 620 you have to clearance a frame rail in to make room for the bag. A piece of big pipe cut in half works well. Someone already mentioned Ratsun.net, there is a thread on there by Slammy and a few others that have bagged a 620.