The Young Allen will of 1774 definitely names Coleman Allen.
In the LDS microfilmed records of the earliest wills of Wake County, Will Book 1, the wills have been transcribed by the local DAR chapter at some time in the past so I have not seen the handwritten original will. This will is recorded at WB1 Pg52 just as listed in the North Carolina MARS listing which indicates that the original is in the archives in Raleigh.
My only problem with this transcription is that I believe an error was made in listing one of the sons as "Robin".I believe this may have been Reuben Allen who was a resident of Wake County and had an early grant in the Fish Dam area along the Neuse River before he moved on to Elbert County GA.
I have photographs I took of this transcription with my digital camera that I would be glad to email to you if you want.