owner says its a 1948 Allis-Chalmers Model D, it just looks a little newer than that to me.
Yup, it's a D. However, D production was from 1949 to 1971. I'd say it's early to mid production because the backbone is pipe (should be 8"). In 1961 they went to square tubing on the D.
That is a nice restoration. There should be a brass plate with the serial number on the outside of the chanel frame on the right side about where you climb on and off the machine. I have a list of the serial numbers for each year and could tell you what year it is if you can give me the serial number.