If you get these heads and intake, I would suggest a few things: send them to someone knowledgeable to have them checked out. Have the valve jobs checked for depth and run out, have the guide clearances checked, have them mag'd, and then gt them flowed. I have a feeling that being set up for .900" means more than a spring change. The valves must be longer than stock for the added installed height. Plan on valves, which means I would plan on a fresh valve job. You'll be lucky of the guides pass inspection. I would not run more than .002 to maybe .0022 guide clearance. For me, anything more than that is "out of service". Plan on springs for sure, which probably means new retainers and some sort of spring locator. If these heads have 3/8 valves, this would be a great opportunity to use some 11/32 valves and save some weight. Accurate flow numbers, whatever they are, mean you can get with someone like Chris Straub and really get the most out of whatever you decide you want to do; build a pump gas street engine, or something full race. He is one of the most talented cam designers I know when it comes to "odd" flow characteristics that some of these older factory heads have. He has cammed some of the most powerful FE's out there. In the end, don't worry about flow or porting or stuff like that...get the heads in as good a mechanical "blue printed" condition as you can. IMO that's where your money will be best spent and you will best preserve the value of the heads and get the best/most performance out of them.