What freewheel for 5 speed Shimano SIS?
 

Working on a friend's daily commuter bike. An old Univega.

The drive train is pretty worn out. Freewheel cogs very worn, chain very worn, not sure about chainrings, pulleys worn, shifting just acceptable but not great.

Thing is, the stem shifters and derailleur are five speed Shimano SIS, which I know nothing about. If I get him a $13 SunRace freewheel like
Sun Race M2A 5-speed 14-28 Freewheel Black/Zinc28 in Tree Fort Bikes Multi-Speed Freewheels (cat1404)
and a generic six/seven speed chain, will that index with his shifters?

Rest of the bike is solid. Trying to keep it running on the cheap. So want to avoid changing shifters or derailleurs if possible.

I would expect that if it conforms to the 5.5mm "standard", it should index fine. Might need to turn the barrel adjuster one way or the other...

Shimano 5 speed SIS does conform to the standard, any Sunrace or Shimano freewheel will work.