softer, shorter than normal shocks avail?

I have a street rod that is using rear shocks that are from a 66
mustang -- this is a bayonett style unit with specs that are pretty
typical....a lot of cars use this.  the ride is way, way too harsh on
poorly maintained roads.  the springs are quite soft...so soft that
they compress the shocks about 2" down...however the shocks are not
bottoming out.  they can't bottom out because they're just to stiff
for the light car (it's a fiberglass model t).

anyone know offhand if there is a shock absorber that is about 2/3
the
height and 2/3 the firmness of the shock?  i have the koni adjustable
versions on another car...but when I set them to the appropriate
softness and try them on the steet rod, they're still a little too
tall (compress a little too much at a stand still).


i'd prefer to keep it bayonet-style, so the rear suspension/mounts
don't need redesign and/or welding.