I do a lot of these heads useing some small block Chevy valves that are .200 longer than original.  That will give you a valve length verry close to the original Allis ones keeping your valve train geometry and push rod length correct.  I ream and sleve the original guides with a repair liner to accept the smaller stem Chev valves so no use wasteing the money on new guides.

 

I usually buy 2.02, 2.05 or 2.08 intake valves and cut them down to what the engine requires and 1.6 or 1.625 exhaust valves.  Don't let some of these goons pull your leg, it's easy to put to large of a valve in these heads and end up with velocity issues for what the rest of the parts can support.  I've done some heads for some real tough and dominant large Div 4 and 5 engines and put smaller than expected valves in.  The manifolding and carburation just can't keep up. 

 

I have a couple sets of valve, spring, retainer and keeper sets on hand if you want to get everything at once or I can give you the part numbers for the stuff.  You don't have to spend a mint on the package, the valves are only about $10 each. 

 

If you want I can post  or send you some pictures of the parts, side by side to compare the length and I've got a couple heads done and ready for their owners that I could show some of the little tricks and things used.  I'm out in the fields a lot and don't get on the computer much right now.