Hi Black River,
If you'll check some of the earlier topics that were posted on SSS you may find the information you are looking for on the best OAL for your Spencer 56-50. I have the Taylor in .45 Schofield, so can't really offer an opinion. You might try to contact one of our members who shoots the Taylor 56-50...they have commented on those posts dealing with the 56-50 Spencer, click on the aliases and send them a PM.
Hope this helps.
Let us know how Taylor helps you with your other problem.
Two Flints