Homemade hybrid

Looking for helpful info on building my opel close to the 75MPG CAR found in1975 mother earth news.I plan on using forklift motor and 700 amp controller
with briggs motor powering generator.

Sounds cool - similar to what I have in mind. What size generator are you considering? Is it to extend the battery range, eliminate batteries, or eliminate plug-in charging? B&S has a lightweight 34 Hp diesel that only weighs 225 lb.