I have since done additional research on John and can offer the following info:
The muster roll I have is for the Veteran Volunteers under Lieut. Col. Dane - 5th Pennsylvania Reserve Volunteers, 3rd Division, 5th Army Corps, It is dated December 23rd, 1863. There are 5 names listed on it one being John Heinlen, a private born in Lycoming County, PA who was 20 years old on the date of the roll. He listed his occupation as a soldier He enlisted at Cattlett's Station, VA (near Manassas per the roll) for a period of 3 years. He had dark hair, dark eyes, light complexion and was 5'5" tall. His film number for his records in the national archives is M5554, roll 52. He was originally in the Pennsylvania 34th Infantry wherein he enlisted on 6/21/1861. He was killed at the battle of the Wilderness on 5/9/1864.