compare two results from the same table

i have two results from the same table that i would like to compare. below is my query and the results i want to compare

SELECT tblItemRoutingBOM.ItemRevID, tblItem.ItemID, tblItem.PartNum, tblItem.ItemName, tblItem.ManufacturerPartNum AS [Mfg Part#], tblItemRoutingBOM.Quantity
FROM tblItemRouting
INNER JOIN tblItemRoutingBOM ON tblItemRouting.ItemRoutingID = tblItemRoutingBOM.ItemRoutingID
INNER JOIN tblItem ON tblItemRoutingBOM.ItemID = tblItem.ItemID
WHERE tblItemRoutingBOM.ItemRevID in (61,70)

as you can see i am returning two records using the where clause

ItemRevID, ItemID, PartNum, ItemName, Manufacturer, Mfg Part#, Quantity

61,121,331503,.233 Aluminum Sheet,,1
70,121,331503,.233 Aluminum Sheet,,3

now what i am looking for is to combine these two together into one row with the following added.  two columns for each QTY, QTY1 = 1 and QTY2 = 3 with a third column added that is the difference between the two QTY Diff = 2

Any thoughts?