You should have a 50 ohm dummy load (old Heath Cantenna, MFJ products, etc.) rated to handle this power. Never tune up or test amplfiers into an "active antenna" system - normally does not provide a standard 50 ohm load across all bands - and creates QRM on the bands.
Before you "bring it up" you should read Bob Norgard's SB-200 Rebuild Notes (with photos) http://home.gci.net/~rnorgard/ampnotes.html
Since these amplifiers are at least 20 years old, some component replacements are "automatics" for trouble free operation.
Bob covers most of these, but changing the HV electrolytics, meter protection and the soft-key mod are the minimum "refresh" for my work. Tube filament voltage is an issue with soem amplifiers.
572-B tube replacement will vary greatly depending upon the condition of the tubes within the SB-200.