Water pump difference

You can use whatever T-cover and balancer is currently installed; BUT
you may need to make two new TDC marks wherever is convenient; one on the cover and the other on the balancer. This will now require a dial-back timing light to check the all-in timing. Another option is to install a timing tape, and then you can use a standard timing light.
This is Not a big deal, I've done it a few times.
Depending on your engine specs, you may need a Hi-flow waterpump, and AFAIK know, they only come in the aluminum housing late-style pumps, anyway.