Re: And the only lap big enough for it ..
Well, to get things started I've got a 256K Core memory array from an IBM S/360 Model 50 in storage. It is not mounted in a frame. It weighs about 500 pounds, is roughly the size of a three drawer file cabinet, and (from memory) it runs about 3,500 watts.
This document might help you on your quest:
http://www.bitsavers.org/pdf/ibm/360/fe/GC22-6820-12_System_360_Installation_Manual_Physical_Planning.pdf