[rotorwrench]

If the removed valves were in the middle of the adjustment range dictated by the adjustable followers then their length could be used but I would measure them all and find an average to settle upon. It's not too late to check this before the grinding process begins. The measurement should be taken from the top of the valve seating surface and not the overall length. A person can only use overall length if they compare with the new valves. Wear and resurfacing can take a lot away from the face of an old valve. Hopefully, most of your old valves are the same length. I have tools for measuring distance from the valve seat to the follower but not all shops have the old flathead stuff.

Are your new valves pin type keeper or tapered lock type?. I also worry about valves that are all stainless steel. The stems can sometimes gall on these unless there is plenty of clearance with the guide. Snyder's recommends .010" clearance but that is more than I would like. If the guides are relined with brass or bronze sleeves then they won't gall. If the stems are steel and the heads are stainless then there is no problem. A magnet will tell. Some folks use the Ford Y-block valves but they are tapered lock type. If you prefer pin type then those are out. There are also oversize valve stem concerns. Later engines don't go oversize. Talk to your machinist and find out if he is experienced with this antiquated way of engine valve work. It would help if they are experienced and know what to watch out for. Hopefully your tappets are all a good fit in their bores. They have oversizes for them too.