Fred, a hearty endorsement! it predates the 076 which is an extremely reliable hard working powerful saw based upon the 075. Same displacement, 111ccs, and I think basically the same saw, except that the 075 might have less anti-vibe features, and I don't think it came with a chain brake. I've had three 076s, and still have two, very much alive after over 25 years. Great saws for milling btw. Something uncanny about the starting ability of those after sitting a very long time with old fuel. I've had the 076 both with decomp valves and without, and they can be painful as you say, without the valve. Kind of overpowering one and not giving it a chance to kick can help when starting. If you get timid with it, they surely bite. I think of the 075 and 076 as great saws, though a bit on the heavy side, but I don't think unreasonably so for being all metal with big gas and oil tanks. I still use my 076 when big wood comes along. Definitely restore it if there is a mind to, your bro will be glad he did, and an honor to your dad. No way a lemon, a fine example of a different era that will still do the job for you with big trees, and once it is in the cut, a very enjoyable saw to use, really hunkers along and cuts wood. Only drawback I can think of is that the filter can load up quick in dusty conditions, nice to have a spare with you like when milling especially.
Gary, 'gasoline', likes those saws too. I wouldn't expect parts to be too hard to find if needed, especially if the 076 ones fit as well. Pretty easy to work on, except getting that black hard rubber or plastic covering off the rear handle if you need to, is a batch. Immerse in hot water for awhile to make it pliable.