I#ve just logged in, amazed to see this puzzle already moved to Expert. So I just tell you what I#ve found out so far. Sorry, if there are some repeats to former solutions.
#1 Lancia Omicron, 1928, six-cylinder-engine of 7.1 litre
#2 1942 drawing by Raymond Loewy for Greyhound Transcontinental Lines
#3 Versare Montreal Type (with arch roof), 1925-1928, electric motor at each end, electricity 4-cylinder Buda engine
#4
#5 Opel Blitz 3t Articulated Bus, Opel 3.6-litre engine, built 1938 by Fahrzeugbau Schumann GmbH Werdau for Dresdner Straßenbahn AG
#6 Viberti Monotral CV61, 12 units built in 1961 for the centennial exhibition "Italia '61" in Torino, Fiat 413 engine with 10676 cc and 180 hp, bodywork by Viberti
#7 Austin K8, ca.1950, bodywork by Kenex?
#8 Berliet PCMR-E, built 1968, 26 built in 1967 and 1968, ex-RATP (Paris Transport), Berliet 6-cylinder-Diesel-engine, 135 hp, Berliet works body
#9 Ashok Leyland double decker bus in Mumbai, India, in service for BEST, coachwork by Antony Motors Pvt. Ltd.
#10 Mercedes-Benz O 305 double decker, BUSAF bodywork, built 1977 to 1985, picture taken in 1994, in service for Germiston City Transport, South Africa
#11 Büssing DF 64, built 1964/1965, the pictured one (BVG #1658) put in service in Berlin on December 29, 1965, body by Gaubschat, Berlin, 29 buses built, engine Büssing U7, 150 hp
#12 1935 Drive Movie Bus, built for the Paramount Studios, the lettering says "Jack Conrads Band"
#13 Mitsubishi Fuso New Aero Queen III KC-MS822P High Deck Coach, 2001, in Yokohama for Kokusai Motorcar
#14 Greyhound
#15 Sunbeam MF2B trolleybus, 1954/55, in service in Kingston-upon-Hull, with Roe 54 seat highbridge bodywork
#16 Golden Dolphin, built in 1956, supposed to have had a gas turbine engine (but uncertain if ever installed), plastic body by Viberti
#17 Mercedes-Benz O 10000 Überlandbus, used by Reichspost, 1937, Mercedes-Benz six-cylinder-11.2-litre-engine 150 hp, 244 units built, body by Mercedes-Benz (Karosserie Sindelfingen)
#18 Henschel HS 140 N , 1953, in service of the Spanish Viajes Meliá, "Reisewagen" body by Trutz
#19 Cyclops, star of the 1976 movie "The Big Bus", supposed to have a nuclear engine, created by production designer Joel Schiller
#20 Lancia Trolleybus, 1967/68, CGE electric engine, in service in Porto, Portugal
#21 Sentinel Landmaster Mark IV, 1955, body by Bellhouse Hartwell of Westhoughton Nr Bolton, in service for Blue Cars
#22 AEC Regal IV, 1953, with Gurney-Nutting body
#23 Renault Galion, 1952, in service for the Spanish ARESA, probably body by Heuliez
#24
#25 Henschel HS 200 UN for Continental Trailways, 1956, Cummins Diesel engine, body by Kässbohrer, in service on the Denver-Pueblo route, predecessor of the Eagle
#26 Leyland Atlantean, from 1967, in service for Storstockholms Lokaltrafik, instead of tramways, coachwork by Leyland's Park Royal Body Division, Leyland O.600 Diesel engine
#27 Yellow Coach Model 735, built for Fifth Avenue Coach Company in 1938, which took 160 of a total 300; 616 cubic inch GM engine, later converted to diesel engine
#28 Büssing Senator 25 DD, 1964/65, in service in Stockholm, engine and body by Büssing , RHD (later rebuilt for LHD)
#29 Twin Coach
#30
#31 Büssing Aero 1-1/2-Decker, body by Ludewig, Essen, 1955, in service in Bielefeld , Germany
#32 Mauri 6.3 on Fiat 416 chassis, 1966, body by Mauri
#33 Ashok Leyland Articulated Trailer Bus in Bombay for BEST, 1967
#34 Jiangsu Flxible CJ6100SLC3HK Double Deck Transit Bus, 1999, in service in Shenzen, China
#35 AEC Regent III, 1954, in service for Carris Lisbon, Portugal, body by Weymann
#36 Lancia Esatau ? with Viberti coachwork, ca.1967