The 74 Super Beetle has the larger 1600 engine (Actually 1584cc) and will definitely not get 35MPG. More like 25. Maybe 27-28, if you have the manual 4-speed, but the 3 speed, or "manumatic" will not do even that well. Still a great car though.
http://www.superbeetles.com/faq.htm has a lot of good information on them. (The main site as well.)
Stock is 1600 cc or 1.6 liter. The bore and stroke are 85.5mm and stroke is 69 mm.
The biggest difference is the 74 has energy absorbing bumpers that the 73 is lacking.
between the rear wheels
Someone put one on it.
NO
check jbugs.com
Mine didn't have any.
1974 was the first year of energy absorbing Beetle bumpers. You can't use earlier bumpers on 1974s.
Machine 7 or Just aircooled
correct it will fit. be sure to take lots of pictures before you pull all of the wires off. so you have a diagram of where they go after.
Replace the flasher relay if the lights come on but do not flash.
Call a locksmith he can make you one on the spot.