Our race valves are produced in EN214N steel and are stellite tipped and use the later narrow, single collet groove and current valve head shapes. They are plasma heat treated to eradicate wear from unleaded petrol and are suitable for our 12G1963 or C-AJJ4037 guides.
As it is possible, even common, to swap one head for another on 1275 engines, it is quite easy to become confused. Be aware that if the head has been worked on previously, it may have oversize valves; it may have undersize if seats have been installed. Unless you are 100% sure what is in your cylinder head, it is a good idea to remove a valve for accurate measurement. There are two lengths used (nominally 3.52" & 3.57") three different keepers, (wide, narrow, and three-groove) and many different head diameters. These longer valves are for 940 or later head castings.
Note that all variations of the 12G940 and the latest CAM head castings all use the following 3.57" long valves.