Dlotz Here is the things I see wrong with the pictures,
If you had new guides install in these 40+year old heads they where hammered in instead of pressed. Maybe air gunned. I have not been pressed guide cracked like this. The clearance to fit could also have been too tight and cracked them. The only important thing is that the guide and valve have the correct clearance and
oil gets to this location. The tops of the guides are most of the time dressed up or cut for new seals. I have seen motor with this problem run 150 passes at the track and not fail. Little blue smoke up startup is all. Would I have this in my motor, NO if I sent money for a complete valve job to be done and this was the returned product.
Valves Looks like they where cut down to fit the seats. You said something about having different heights on the valve stems. This is going to happen if valve seats are replaced and have to be machined into the head. Some seats may be installed .060" deeper to find good clean metal for everything to hold and be staked too. The problem is 40+ year old heads and a machinist trying to do the best job with what was giving to him. If you are looking for perfect, buy new parts or spend alot of money for old stock OEM parts you get in a box. The other thing is to go to aluminum heads and remove the logos on them. Paint them and no body will know. I would guess the valve where cut down and ground to try and match your height problem also. You can get caps for the valve stems in different sizes than might have fixed your problem. I would not be happy with the money you spend, BUT there are 3 sides to every story and I have only heard 1/3. If you can get another set of heads, Do that. Have the heads check, If they look OK, install new
oil contol seals and maybe HAND lap the valves just a little to reseal the valves to the seats. Make sure the heads are flat and have not been shaved .100". If this is a race motor, BT heads and mill the ends. Rick L. Ps If the machinist had frozen the guides and heated the heads this cracking of the guides wouldn't have happened. Same repair as installing cylinder sleeves in a block. Alot less force is needed.