distributor hold-down prevents timing adjustment?

What I mean is that low and mid-RPM throttle response will be degraded.... as you say, the result of less low end torque with the retarded cam timing. For most daily uses for the /6, restoring the cam timing to as-new will make the engine a lot better to drive.

I replaced a worn /6 timing chain that was allowing 4-5 degrees of retarded cam timing and the result was as said: much improved low and mid RPM throttle response. So I'll disagree with the idea of not replacing a worn chain .... for most drivers, it will be a very noticeable and worthwhile improvement.