Taxidermy is in Experts 3.5, both as a subclass and as a skill. It allows characters to create mounts from most of the creature types (those excluded are obvious). What it doesn't do is allow for patchworks or replicas. Both of these can be useful in golem construction.

Patchworks are mounts that are made from two or more species. Usually they are called humbugs or something similar, but I prefer the term patchwork. To make a mount from two species within a single monster type, the DC increases by 5 and the cost by 1.5 (which will increase the amount of time as well). To make a patchwork mount from more than one monster type, increase the DC by 5 for each additional type and the cost by X2 (so 2 types is twice as expensive, three types is four times as expensive, etc.) Golems made from these mounts should have some additional extraordinary powers related to their various body parts.

Replicas are mounts that look like one creature but are made from another. These require the use of alchemy to reshape bones, color skin or scales and make other changes as needed. One could even make a human from the tissue of canines, dragons or fish- it just costs a lot and takes much longer than usual. If they bodies do not have bones, then it becomes an epic task as make them from muscle or skin is astoundingly difficult, but still possible. Why would someone do this? Well Polymorph Other (or Baleful Polymorph) doesn't make permanent changes- the victim reverts upon death. And some wealthy people want fake dragons (usually made from giant lizards or basilisks) or other monsters for their castles but don't want to actually find and kill one. Strangely enough, Frankenstein's creation was at least in part a replica- there is reference to Victor using parts stolen from slaughterhouses. I wonder what the author was trying to say in that one tiny sentence in the novel? As for the rules for making replicas, I would limit them to those with a new feat:

Create Replicas

Prereqs: 12 ranks of Craft (Alchemy), 12 ranks of Craft (Taxidermy), Int 16+

The character can now create taxidermy replicas.

As for the DCs and costs, that is too complex as there are many variables to consider. GMs will simply have to determine those on their own.