Hello,
In this case,
55 analog input:
You would still need 2 32 channel modules (SCXI-1100, 1102/B/C, 1104/C).
5 analog output:
Would only require 1 6 channel module (SCXI-1124).
18 Digital I/O:
Would still require either a SCXI-1162 (DI), SCXI-1163 (DO), or a combination of the two.
Worst case, this is 5 modules that you need to control. You would need at least 6 slots including the SCXI-1600 controller. The SCXI-1001 is a 12 slot chassis that would work for this setup.
Keep in mind, that if you do not need any signal conditioning, you can achieve this channel count with 2 PCI/PXI-6259s. They have 32 AI, 48 DIO, and 4 AO channels each. For more information on this product please click on the following Link.
http://sine.ni.com/nips/cds/view/p/lang/en/nid/14128
Also, I can have you local Field Sales Engineer (FSE) contact you to discuss your options if you would like.
Regards,
Sean C.