Well, I'm shocked at the varied opinions
Tube, lever, friction, gas, adjustable. It's a damper as we all know. Consider the weight and the desired control. Consider your normal driving conditions. I live in a MI county that has no road money so my roads suck.
IMO, it's hard to beat the real deal. It can be copied with friction shocks but not for long. I can't speak to a tube conversion, but I'm thinking the angle of mounting will also have a lot to do with the shock's performance. Think about how the axle reacts to a bump or drop in the road. It surely does not move straight up and down. Do these new kits consider that? The more linear the action is to the axle the better the damping. If the shock is too vertical it will dampen more than you want it to because it's "moving faster than the axle". Make sense? This is the reason the ball joint links connect the levers to the axles, so they can offer linear damping to the natural twist of the buggy spring mountings. Someone mentioned Speedway. Good idea. Take a look at some of the hot rod set ups and note the angles that the shocks are mounted when using the single spring. Some of the more pricey front suspensions are very well designed and can offer some perspective. I personalyl would rather have the OEM stuff, but I can see that prices for those parts has become a bit high. I can buy used 30s Packard shocks cheaper sometimes!