Is the Highway Hawk Brake Cylinder Cover that was designed for
VN750, VN800 and VN1500 compatible with our bikes?

The stock cover has a protrusion that goes into the flluid and the Highway
Hawk cover doesn't. I was wondering if the reading on the sight glass would
be accurate with the HH cover? and if the HH cover is usable on our bikes?

Anyone have a Highway Hawk Brake Cylinder cover installed?

Do you mean the rubber diaphram in the stock cap?
I would guess you'd need to put that onto the HH one.

Most chrome covers I have seen go over the stock one. You remove the screws and put the new cover on top and reattach.
How about this version.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=004&sspagename=STRK%3AMEUS%3AIT&viewitem=&item=140121250159&rd=1&rd=1

Haven't looked yet Hyper, but I think your right on again.

I have one, You do remove the rubber and swap it to the new chrome cover.
Thats what I did and worked great for 2 years so far.