Any of the OLD GMC pickups, busses, etc. that used the V-6 GMC engine (spark plugs in the center valley) and stick trans. They are getting hard to find. The last three I scored were at a tractor/heavy equipment yard.. I don't think Chevy used these engines..
The Camaro-Firebird ones are more common and will work well. The reason I like the GMC ones, is they are easily rebuildable. Lots of travel.