I am looking for a service manual for a rig I acquired. I've found listings
for it at the following places:

Ham Radio Manuals by WB2JKJ - Icom Yaesu Kenwood Heathkit Drake and more!

Amateur Radio products and equipment by rossdist.com

Vintage Manuals, Inc. Catalog

Manual Mall: Owners and Technical Manuals for Manufacturers JA - KX

Has anyone had experience with any of these, and if so, which would you
recommend?

73,
Bob AD3K