Main Motorcycle: T140 E
Join Date: Jun 2009
Location: Reading Berks UK
Other Motorcycle: 56 Plunger Tatty Cub
Extra Motorcycle: CZ winter bike
If it was me, I'd use a 750 from an oil in frame as they seem to be less valued than the earlier bikes.
I don't know if you've ever built a bobber, but the cheapest way of getting a job done (I'm told) is to buy a whole bike that maybe needs work, or has had a prang. That way you'll get the wheel, forks, brakes and engine and sourcing parts is easier if the whole bike started say, as a 76.
The OIF can make a nice bobber - or go earlier if you want a "normal" frame - unless you plan to build one
Generally, the bikes got better - the early OIF had a high frame