The SSM ones are more or less junk. I have them on my car too along with the traction bars. More or less the SSM frame connectors are 2 straight pieces of square tubing that you mickey-mouse onto the front and rear subframes with a few gussetts. They hang down and if your car is lowered (like mine is) they hit on stuff occasionally. Not really worth the $122 I paid.
Stumpy took the idea a few steps further and really makes a nice clean tight connector. I'd buy his, and probably go with a weld-on set if you're a welder. Once they are on, you're gonna want to leave them on anyways and welding them in is just a bit stronger.
The SSM slapper bars, I really like. They work GREAT. They are straight pieces, not curved but they do stay tight to the spring, not hanging down like some Lakewood universals do. I had chrome Lakewoods on a '78 T-Top Cobra I had and they didn't fit bad either... not hanging down.
But since SSM is no more, Stumpy's lift bars are the ones to get. They are basically the same as the SSM bars.