I've got the SCSI-IV too and it's an arse to upgrade/maintain.
Luckily it is a SCSI-2 adaptor so will ACTIVE terminate itself so you only have to worry about terminating the hard disk as has been mentioned.
To 'terminate' a SCSI device is just to stop the radio noise from reflecting up and down the wire due to the speed of the electrical signal.
Usually the black header on a 50-pin IDC ribbon has a raised bit on the top bit which is supposed to be facing upwards. A 50-pin IDC female on an adaptor should then have a notch to align with your male.
Try to keep the number of adaptors, heads etc. down as this increases RF reflection. Always make sure that the heads of a ribbon are 10cm apart from each other (a cable should be made this way) and keep the chain below 3 metres long.
I'd stay in Asyncronous mode and don't try Synchronous untill you have a firm grasp of SCSI and the necessities for a high speed connection.
At this point I'm in the same boat as you so this thread should be interesting.
