I would like to purchase for my D6B serial #44a1360 a hydalic parts/service manual. The serial #on the hydralic tank is 39f632. Which book would I need? For example is it a 163 or 182 system or what. What would be a good place to find such a manual? Thank you.

You need to be looking for a parts book for the #161 Hydraulic Controls that covers your 39F serial number.
The Cat designations are a little confusing and not always consistent but in general the first digit is the style of installation, the second digit is the tractor designation (in this case 6 for D6) and the third digit may designate the number of valves but for the D6B there is only the 1 designation even though the unit may have one, two or three valves.

The typical Parts Book will probably cover many models so you will have to be on the lookout for your coverage.
I do have a manual for the 44A but it is for later serial number 44a1600 up and controls units 36F1-up, 48,49,55E series,92,93F series and 62G series. If you are stuck for specific information I can post diagrams if you like, I doubt that they changed all that much.

Need to make a correction:rolleyes:
Got to rooting around in my stuff and found the Parts Book covering the early 44A.
The 39F1-up serial number is listed as a 163 Hydraulic Control.
The Form number is 34311 (replaces 33808) and covers 163, 165, 182 & 192 models with serial #'s
70E1 to 70E384
38F1-up
39F1-up
41F1-up
42F1-up
69F1-up

I'm not interested in selling but can scan and send specific pages if you like.