There are a couple of rebuilders other than BB. They all have the specialized tools to "take apart" the shock (i.e. typically a 4' specialized wrench which "encircles" the cover.)
And even so, the interior condition of the shock frequently doesn't warrant anything other than bushing out and re-building.
There has been some information about rebuilding shocks published. There are plugs to be driven out and replaced, holes to be sure they are "clear", and internal parts which are not by themselves "rebuildable" and have to be replaced wholesale with new oversized components. "Billet" is frequently mentioned for these parts.
One rebuilder will take on shocks but will not guarantee 60-40 action (which is correct) and the shocks frequently end up 50-50. (or 100-0)
So it's not really a task for the home-rebuilder - even though the parts houses frequently sell the entire "gasket set" to those in learning mode. A good write-up of the challenge is shown at
https://files.secure.website/wscfus/...l-a-shocks.pdf
There have been houdaillie type shocks "recreated" by various makers. I believe it was M&S who were less successful, but another whose name escapes me was highly thought of.
And - an alternative might be "friction shocks" which served well as replacement units in the 40's and 50's. Friction shocks MIGHT be considered inferior substitutes, but they actually have some theoretical recommendation if one considers them in "optimal vibrating system" terms.
AND - there are the various Fiat and other shocks (mostly European lever shocks) which can be used, sometimes without modification.
Or even Tubular Monroes - with all the modifications required to your chassis/running gear.
If you decide to go without shocks - DON'T lubricate your leaf springs.
Joe K