Hi Stan,
Here is a chassis I recommend for your loco it will be an exact fit and does have the original style plastic drive rods. It does have the latest Version 5 chassis:
http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_69_671_669&products_id=4093If you want to use the Anniversary 4-6-0 chassis with the metal valve gear and drive rods there may be a spot or two where some trimming may be needed, but the chassis should fit OK. If Your old 1992 Bachmann plus loco has the single switch boiler door, you may want to get a boiler door with two slots one for the smoke switch and one for the polarity switch.
Boiler Door:
http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_69_671_148&products_id=9427Here is the one I like because it has the metal Walshearts valve gear:
http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_69_623&products_id=4084Both of the above chassis are current on sale. I always recommend doing the chassis replacement in one sitting and taking reference photos as you disassemble the old one. All in all a fairly straight forward Job.
Bill