I attached the Persci 277 to a known-working Cromemco System 1 with 16FDC drive controller. The drive did not respond, but I did not confirm for sure I had everything correct to cause the system to look to the drive to boot it.
I referred the customer to someone who has an IMSAI turnkey system. Assuming I am correct that the replacement ROM (V 1.1) is not compatible with the Tarbell controller attached to a Persci 277 drive the next step is to find a controller and drive that is compatible with the turnkey system running ROM 1.1.
I could have but did not have the time to attach the Persci 277 drive to my Cromemco System 3, which already has Persci drives (299's) to see if the 277 works, but I gave this system back to the customer.