Thanks all!
I doubt I'll order a kit: just get the parts & build it. Thx for the tip on Ceriatone docs, I forgot about them. I had a Ceriatone DC30 & it was a fantastic amp.
Chris Merren hand builds his own transformers & is a longtime specialist on old Marshalls. He used to work for NASA & really knows his stuff. He also makes Neve, McIntosh, and Hiwatt replacement transformers:
http://merrenaudio.com/marshall_output_transformers
I have one of his OT's in my '66 JTM100 and it's amazing. So I bought a JTM45 OT with intent to build one, at some point.