The Western Auto Revelation brand Model 150 is indeed the Marlin Model 49 semi-automatic, .22 caliber rifle.
You can go to Numrich Gun Parts Corporation for a parts drawing. Go to www.e-gunparts.com
then on the left side of the page click on the "M" which will take you to a list of manufactures that start with the letter "M", click on Marlin, the scroll down to "Model 49 Rifle". There is a new diagram online there which you can print out if desired.