Hi,
I have used stock shafts, rockers, and clips for years with no problems to 8000rpm.
That's no ratio rockers or weird rocker geometry etc, otherwise I don't think it would have worked.
Especially on a stock 1600 with stock cam and rockers, you wouldn't be revving it past 5K, so I wouldn't see you having a problem at all, if I never have.

Having said that, as Tom says, $30 is $30, and put together properly, a bolt together setup works fine too.
I say put together properly, as I've seen sets on other people's cars years ago that have an allen screw to locate the middle spacer on the shaft, the allen screw undoes and falls out, then the spacer thrusts against the shim washers and binds the rocker, which in turn holds the valve open nicely for the piston to come and smack it, resulting in a bent valve and a little bit more!
