If you're not familiar with this this site, it's a great resource for researching pulp magazine covers and general publication information, including title changes.
It aims to be a complete survey of pulps of all genres; sf, horror, mysteries, etc. and includes links to sites of interest and has links to the indexes that have been used to verify information. It has an AMAZING array of covers that you can view.
Click on "All magazines" and you'll be taken to an alphabetical listing of the titles, broken down into bit sized chunks; "Air War to Amaranth" for example. Clicking on a section will bring up the list of titles with information including the chronological run of the serials, and on the far right a "issue checklist" option, which indicates whether or not the covers have been scanned and uploaded.
Clicking on a specific title will, of course take you further into the record and will give publication information; which title was sold to what publisher and when, who the editors were, etc.
Click on "Issue checklist" and this is the glorious part; this is where the covers are laid out as a mouthwatering buffet to browse through. And of course, clicking on a particular cover will bring up larger pic.
The fellow who runs the site is always looking for scans of missing issues, but the site is considered so reliable that sf libraries use it as a reference resource.